I don’t know, I think it’s extremely obvious which brother is more canonically “fem-coded” (even if unintentionally) just by the way that they’re perceived by their own demographic (cishet white men). I’ve noticed that they tend to idolize Dean way more, because he’s got an ultramasculine womanizing personality, likes cars and drinking, and fits into the protector role (when it comes to Sam) that they often fantasize about.
Him having a “feminine/pretty boy” face barely affects things beyond a few jokes made by primarily *women*. Sam on the other hand is constantly made the butt of the joke in a seemingly misogynistic/homophobic way, I would not go as far to say he’s a “victim of misogyny” but the way he is treated in the show AND by the fandom is a byproduct of societal misogyny.
The constant comments about his hair, the way he eats, how him being compared to women/called a woman is supposed to be “comedic”. Every single one of his actions are magnified and examined so that he can be punished/scrutinized for it.
It is also pretty much coded into the show from the beginning that Sam is the “passive” one, it comes from Supernatural originally being a Gen-X power fantasy where the stoic macho man guides and influences the soft educated, one could even say ‘liberal’ younger man into a life of badassery and all-american roughness.
One thing I barely see mentioned is that this show was also watched by older, pro-military right-leaning audiences too, they dislike Sam for the same reasons that so-called “progressive” spn fans do, except they think it’s because college is a gateway to progressivism, that it’s for softies who can’t do REAL manly jobs. They think of him as a coward for running away from John, Dean, and the whole hunting lifestyle. The truth is that non-shippers (especially the dudebros) view Sam as the less masculine one, because it’s hammered into your brain from the very start. These types of people have no clue what the fuck an “omegaverse” is, have zero idea on fandom history and would probably scoff in your face if you dare imply Dean is anything but a straight man. But they’re more lenient on Sam when it comes to that type of thing, because he IS seen as the “emasculated” one of the pair.
The writers also knew this too, since nearly EVERY time Sam and Dean are paralleled to a couple, Dean is the man, Sam is the woman. “Mallory to your Mickey”, “Bonnie to your Clyde”, Red Meat where Dean is Romeo and Sam is Juliet. They aren’t dumb, this is why the Season 6 role reversal (where Sam was finally seen as the more “badass” one) felt so “wrong” to people, because they’re so used to Sam being feminized in canon. We’re not merely ‘fetishizers’ or ‘ass-pulling’ when it’s literal canon that pushes this narrative.