Thought experiment. Supposing there was a test you could do, cheek swab say, that diagnosed brains into clear categories of 'mind-sex'. Let's say we did this for babies at birth and recorded their mind-sex on their birth certificates alongside their physical sex.
Would that change who should be in women's sports? No, the reasons for women's sports are bodies not minds.
Would it change who should be categorised as women in medical studies? No, that is about knowing what medicine to give to male or female bodies.
Would it be the appropriate categorisation in the teaching of biology? No, female people would still be the ones with ovaries and uteruses.
Would it be the appropriate category for prisons? No, people with penises can rape, can get people with uteruses pregnant, there is a strong safeguarding reason to keep female bodies and male bodies separate in prisons.
Would it be the appropriate category for changing rooms? No, people are less embarrassed getting undressed in front of others with the same body type to them, plus above note about the risks of penises.
So if there is mind-sex, so what? There is also physical sex and it matters.
[ohgod i actually ended up typing that dreadful phrase 'people with uteruses'. It was a thought experiment okay? I'm not proposing we use the phrase in the real world]
[why would we even call this new biological marker something to do with sex, rather than an interesting brain feature that influences people's personalities and interests, or a physical indicator associated with body dysmorphia disorders?]