Angel also said they never lied about who they truly were, so I think I'm coming away with the conclusion that Angel and the real Dr. Aspen are both non-binary. (Also, I hope they mounted a Dr. Aspen rescue mission after this!)
I also think Angel's gender identity doesn't demand to be engaged with in order for the story to work, in contrast to, say, how TNG's "The Outcast" demands you engage with the genderless J'Naii and what it means that they're cast with all women in a gay parable. On a thematic level it certainly feels like a purposeful choice on the writers part, given that Aspen/Angel spends the whole time talking about the binary in Spock, but I also think it's a fine reading to just ignore that and go along with the story.
I was actually totally surprised by the Dr. Aspen twist, just because I didn't consider it a possibility that Trek was going to do a non-binary or trans villain yet. This franchise has only had Adira, Gray, and (if we're counting balls of energy) Zero in terms of trans or non-binary representation so far, I didn't think we were at the "evil non-binary character" stage yet.
But, as a gay guy, I distinctly remember how boring it was when every gay character was sweet and sexless, and what a fucking relief it was when we had enough overall gay representation that we could start having gay villains again, so maybe this time society is just getting through that cycle quicker?
Yeah, I clarified upthread, but the missing piece for me was that she also identifies as non-binary. I have read about her and seen some of her other work and I only ever encountered her referred to as a transwoman, then I checked her IG and it listed only she/her, so I initially thought this was a case of an exclusively female-identified person being cast to play a non-binary role. Knowing they also identify as non-binary, now the casting makes sense to me.