an instinct to identify with a group based on observable sex traits

So...once again we end up with gender roles, except in more words.

normalize some sort of appearance standards for your own self based off of that criteria

Like...the whole point of feminism is not to do that. Women have nothing to "normalise" themselves according to; they're women regardless of whether they feel like women, whether they enjoy being women or whether they relate to being women. They're female when they're unconscious, when they're dead, when they're infants. The fact that the patriarchy has decided a "woman" is akin to a walking blowup doll or a type of brain you have is a PROBLEM, not a fun thing to validate your gender with. Remove that, and women are still women - male trans people are not.

we naturally see these sorts of sex trait groups form among chimps and bonobos

Oh ffs, here we go again...

it doesn’t seem odd to think that some sort of modified group instinct is operating and creating a sort of instinctual sameness between members of a group that posess similar sex traits

Lovely. Bioessentialism supports patriarchy because chimps, and if women are getting screwed over by it, they should just comfort themselves knowing their gender is being validated by these groupings.

creating a sort of instinctual sameness between members of a group that posess similar sex traits

"It's not gender roles, guise! It's something different that's exactly the same, except not called that!"