In 10x07, Cas was involuntarily attracted to naked Hannah, and no amount of fandom stuff is ever going to change my mind about that.
(Okay, I was exaggerating a bit just to get your attention there.)
But I think he was nervous seeing her vessel naked in a way he was not when she saw him naked. He has to try not to look. He straightens up, like he’s subtly aroused, and the picture on the wall is a whole bunch of erect buildings. Cas stands torn before two modes: duty and lust. (I would say his physical attraction to her is, if anything, a little involuntary and NOT something he wants to act on. I even think his bodily reaction may be why she thought she had a chance post-the gentle letdown he previously gave her.)
(Yeah, yeah…the board could be casework, the skyscrapers Heaven, but this is more fun.)
Season 10 screams painful things about temptation. I think that Cas is being actively tempted by Hannah, and he defaults to duty, as he always does when it comes to feelings. And Hannah? Wants so badly to be wanted. Maybe Metatron was right about her hidden needs: "desperate to be dominated” indeed.
/// Meanwhile, in the same episode, Sam calls Dean out for falling for a (prostitution) ploy. This comes on the heels of Cas's accidental rejection; that is, his response to Dean's "I'm glad you're here," which was "Another time. There's a female in the car." So, Dean goes in search of validation:
SAM: "But [Shaylene] seems, um... Kind of...available. Like too available. 'Oh, baby, whatever you want. I'm burning up just thinking about you.' No, it's not bad, Dean. It's too good to be true.
Then Shaylene shows up and Dean goes for it, because he (like Hannah) is desperate to be wanted. We cut to him being slammed against a wall, and she stops to tell him she has rules. But she means payment, and Dean is so disappointed that he wasn't really wanted.
As it turns out, Shaylene was “abducted” during a vulnerable time and forced to work gathering souls for a demon. (Ouch. Freshly familiar!)
But in a way, I feel like a fun reading of these sexy scenes being back-to-back is actually both of them being "aroused" and neither of them getting what they really crave (emotional connection). Alternatively, Cas secretly wants slippery shower sex and Dean wants Cas to slam him against a wall? Those two things are compatible.
///
As a character, Cas typically withholds his affection out of duty, even when he feels arousal that he could act on.
(It's fine if you read this differently, but I see Cas as being canonically aroused on multiple occasions: as an angel by straight-adjacent porn, by Meg on at least two occasions to the point of wanting to "move furniture around," and by a random human woman on the street after his grace had been cut out. Not to mention his "hopefully more of this" line and hopping happily back on top of April. So, to me, it's not a total reach to frame Hannah as a very real temptation here. I think Cas's "oddity" lies in being attracted to "strange flesh"/HUMANS/demons/“SOULS,” regardless of the whole gender thing. Ergo, as an angel, he's "queer" because he likes flesh in the first place, irrespective of the shape of that flesh.
HANNAH: He wouldn't listen, Castiel. He wouldn't let me go. I didn't want to hurt him. I could've erased his memories, but... It didn't feel right. I thought if he truly believed we were together, he'd give up. And it worked. So, why does it feel so bad? CASTIEL: You did the right thing. You hurt him, but you gave him a reason, something he could use to move forward and make sense of his loss. I had to take my vessel from his family -- twice, actually. Jimmy Novak. He was a good man. He was married, had a daughter...Claire. HANNAH: And? CASTIEL: And it was difficult but necessary. The mission comes first -- always.
But Hannah, suddenly, does not feel that this is the right thing. Suddenly, she's questioning the parameters of the mission.
Deep down, Hannah wanted to act on her feelings for Cas, but in doing so, she hurt Joe. That's a lot of what their kiss was about--stabbing Joe in the heart. She realized it was wrong to take Caroline for the mission and hurt Joe (and if you squint, I agree this could represent Dean). But at the forefront of my mind, Joe is Amelia Novak.
At core, Hannah realized that in wanting a relationship with Cas, it was at the expense of another person's life. And then came the shame of that. This plot works to underline Cas's shame, too.
It underlines WHY Cas is hesitant to stay on Earth, why he won't act on his feelings for Dean, and why he feels he doesn't deserve to. Meanwhile, Dean spins out because Cas, one of the people who truly knows him inside and out, who wants him to exist as an integrated human with good parts and demonic experiences (not all human or all demon)…doesn’t seem to want him. Anyway… unlike with Jimmy, Hannah can still save Caroline, so she does. But it's too late for Jimmy. Too late for Cas?
So, Cas looks up Claire Novak. Perhaps with enough penance, he can at least be allowed to stay on Earth?
///
Earlier in the season, Demon Dean is having freakouts revolving around monogamy and infidelity. In his mind, Dean hunts and only works works works. He's only good for work; that's all there is to him. He "whores" around, because he doesn’t think he’s good enough for a happy life/the commitment he might want.
And interestingly, the back half of season 10 is about the shame teenage girls feel when used by deceptive men for their own personal gain.
Anyway, Demon Dean is bitter about being looked down on, just as much as he's strangely sensitive about wanting fidelity, respect, etc. Honestly, if Dean didn’t seem to actively want monogamy and devotion, I’d be happy to leave SPN alone as the perfect story of platonic devotion or alternative relationships. But Dean’s got hangups about it. He seems to long for a simple, old-fashioned relationship.
He's sensitive about it, and so wistful, as if he's afraid he's ruined his chances from both the party-boy way he's lived his life and the undertaking of the Mark of Cain. (A painful parallel is that Crowley effectively dangled Dean in front of Cain in order to solve a power problem within his kingdom/Abbadon, in a parallel way to how Randy used Claire to solve his debt crisis. Claire was out running odd jobs to make money for Randy, and Demon Dean wound up working for Crowley to make money/souls in the Hell system.)
In 10x07, Dean seems disappointed that he's not even wanted, but when he faces Cole, we see that his self-worthlessness runs deep: "Cole, once you touch that darkness... It never goes away. Now, the truth is... I'm past saving. I know how my story ends. It's at the edge of a blade or the barrel of a gun." Ergo, Dean is “damaged goods.”
///
Anyway, Dean is sensitive about all of it, because it's the one thing he wants (and can't have, because it's Cas, it's Cas, it's CAS).
There’s a little truth in his distraction tactics:
Dean: What if I said I, I didn't want to die... yet. That I wasn't ready. Father Delaney: Are you expecting to? Dean: Always. The life I live, the work I do, I pretty much just figured that's all there was to me, you know? Tear around and jam the key in the ignition and haul ass until I ran out of gas. I guess I just thought sooner or later I'd go out the same way I lived, pedal to the metal and that would be it. Father Delaney: And now? Dean: Now. Recent events made me think I might be closer to that than I really thought. And I don't know; there's things, there's people, feelings that I-I want to experience differently than I did before, or maybe even the first time.
SPN 10x16 Paint it Black
///
Dean and Cas are, in season 10 and 11, struggling with, not just their feelings, but wanting to commit and live together despite their mistakes, and they both feel too worthless/guilty/ashamed to do so.
(We see this idealized commitment mirrored with Caroline and her husband Joe; he welcomes her inside when she comes home, the same way Amelia and Jimmy will welcome each other later this season, in Heaven.) (But Dean? Feels like he's damaged goods. He has no right to ask anyone to STAY with him, much less Cas. And Cas? Feels like he should be in Heaven. He has no right to STAY on earth, much less be together with Dean.)
Season 10 is a lot about the baggage of the past and how it affects the future; nay, how is cancels out the deserving of the future. It will not be until Mary comes back that Dean begins to hope for his own future, and Cas won’t allow himself this until Jack (the perfect earthly-heavenly cause) appears.