What if Mike was finally gonna tell El he loved her and wanted to be her friend in the pizza scene. Think about it. Avoiding the topic clearly wasn't helping him to not lose her, so he had been talking to Will about working up to tell her something hard to hear - that he loves her and wants to be her friend - but he was scared that she only loved him romantically and would leave him. That is, until Will told him that she would never leave him and showed him how much he sees her. That made him feel more secure and like he could tell her how he really felt without her leaving.
Like in my recent post, I misremembered another ElMike moment as more romantic than it was. I thought Mike was smiling when he was about to tell her something in the pizza place and that made me think maybe it was that he loved her. I just rewatched it. He wasn't.
This is not the face of a boy who has been desperately trying to tell El something he knows she wants to hear and finally can. According to him, his fear was admitting it to himself, providing no reason to be scared to tell her as by the time he says it out loud he would have had to admit it to himself already. The face of the boy I just described would be smiling, nervous, but just a little smile like a misremembered - similar to the one he was making a few seconds prior when he said "I missed you too". This is not that boy.
This is face of a boy nervous about how the girl in front of him will react. This the face of a boy still scared shitless that El will leave him, but with just enough confidence gained to do it. He is nervous in this image. He is watching her reaction steadily in anticipation for what he's about to say.
If what he said in his speech was true, he wouldn't be scared of her reaction. He was scared of eventually losing her and having that hurt more because he invested more, not as an immediate consequence of saying I love you. And even if he had been consciously lying, he would not have been scared for her reaction. Hell, the whole argument for him lying in the later scene is that it's the safe choice in terms of how she'll take it!
The image above is of a boy focusing on breathing in and out, watching for El's reaction to what he's about to say. Rewatch that scene. He's nervous. I do think that the van scene gave him the courage and security in his relationship to finally tell her how he really feels. But I don't think that was romantic love like we later heard from him.
And now, just like Will in his lie, he's trapped. Because you can tell someone you trust needs you that you want to be their friend. And he was ready for that much. But what you CAN'T do is tell them you want to be more than their friend knowing it's what they want to hear then take it back. So now he's stuck in this lie again. Because he was ready to tell her. But revoking what he said is an entirely different level to that truth.
And the more I talk, also, (and this isn't required to this interpretation, branch of here if you like), I don't think Mike knows his feelings for Will yet. I think that'll come with the painting reveal. In short, I think his defensiveness comes from an avoidance of the topic that he'll be forced to confront when the painting comes to light.
But this is somewhat a case of Occam's Razor. I don't think they lied that much. Mike's arc was still about not being able to tell El the truth of his feelings before she left so he spent the whole season working up to it and getting over his fear of losing her. I think his focus of this season was El and that Will didn't play into it for him yet, like we saw. "He's oblivious". But unlike we saw, I don't think that he told her that truth. The arc is what we thought it was: Mike working up to telling El the truth, but Mike and Will's arcs this season are parallels in that way: two boys building up to tell someone they love their true feelings, overcoming fear of losing them, only to, when the moment comes, trap themselves in a lie they can't take back so easily.
