That's actually not what's in contention here. Using singular "they" when gender is unknown avoids the old default of "he". Which feminists rightly took as sexi

That's actually not what's in contention here. Using singular "they" when gender is unknown avoids the old default of "he". Which feminists rightly took as sexist. What this is about is using singular "they" when declared gender is known. Whatever people declare themselves to be is what they are. The rest is just mechanics.