We could say, I'm a woman and I can do anything; or we could say, I'm non-binary so I can do anything
But what does “woman” mean? What does “non binary” mean?
If the only meaning of woman is adult human female, then non binary is completely redundant as a concept. Non binary needs “woman” to mean something more - something chock full of regressive stereotypes - in order to have any function at all.
All it means for a hypothetical biologically female “NB person” is “not like the other girls”. And by saying that, the NB person is automatically reducing “the other girls” down to a homogenous collection of outdated tropes that only she (along with other enbies) is cool enough to transcend.
Because at the end of the day, the hypothetical NB person we’re talking about here is still an adult human female. So a word that only means AHF would clearly apply to her. She can’t actually reject her sex; it’s an immutable part of her.
So what she’s (supposedly) rejecting are the stereotypes, or some of them, that go along with being an adult human female. And that means she needs the meaning of “woman” to include all those stereotypes, so that she, in all her NB cool-girl-ness, can demonstrate how different she is.
Regressive stereotype-reifying bullshit.