I think that there are also concerns with safety and dignity when it comes to restrooms. I don't think that there should be some test at the door for a person's sex (so, if a trans person has had surgeries, etc., they can go about their business in incognito mode), but there needs to be an underlying expectation that people cannot flatly identify into spaces designated for the opposite sex, since I've heard of so many cases of predatory men being allowed in women's spaces by authority figures who respond to concerns by deferring to the predators' unverifiable identity. Single-sex spaces exist for a reason - this article (thetimes.com/life-style…) provides what seems to be pretty solid evidence against mixed-sex restrooms (which I think would necessarily include those opened up to gender identity honor codes).