1h later, self-comment bc too late to edit.
Realized I mentioned mirroring on one axis, but not on the other (perhaps more relevant) one - i.e., I also don't know how many trans women there are in women-dominated spaces, and therefore can't really have an informed opinion about whether trans women (or trans people in general) are more likely to prefer spaces dominated by the gender they left or the one they went to.
Obviously, still thinking about this.
Damn.
I'm ashamed I didn't think of that framing myself.
Yep, I'm cis het male. Yep, I studied stem and I program and video game and dabble in motorsport and have experience with in-person and online spaces for all of the above. And yep, most of the trans women I know or have interacted with have been in these contexts. And I've seen a lot of "why are there so many trans women in programming?" "why are there so many trans women in video game dev?" etc.
But yeah, of course I (and the people asking the above questions) don't know how many trans women are in women-dominated spaces, cause we're not in those spaces.
Heck, I don't even know enough about those spaces to posit a plausible example of the mirror phenomenon. Grad school? Fiction writing? uhhhh needlecrafts? Are there forums somewhere where cis women are posting "how come there are so many trans men running needlecraft content creation channels?"?
Anyway, thanks for the food for thought.