I think the whole non-binary thing is an overcorrection of the persistence of gender roles. We don’t need to invent labels if we just make the existing ones broader.
If biology can produce transpeople, It’s not a reach that it’d also produce people who aren’t fully cis or trans. Nature doesn’t tend to be as neat & orderly as we’d like, after all.
But gender roles certainly do need to be broader, it’s true.