It's also worth noting that even if there were such a thing as a female brain, and even if trans women had all had their brain scanned and been diagnosed as having female brains, we would still not be able to see their female brains, only their male bodies.
So even if the female brain theory were proven, which it hasn't been, it would still only be relevant to the question of whether trans women should be placed on women's hospital wards if you are approaching the question solely from the perspective of how someone with a male body and a female brain will feel to be excluded, and completely ignoring the perspective of how people with female bodies and female brains will feel to share their space with someone who has a male body.
So not only is the female brain theory absolute nonsense, it still requires you to place people with male bodies above people with female bodies in the hierarchy of rights.
Now, I wouldn't generally argue that society shouldn't meet the genuine needs of minorities simply because they are small in number and taking them into consideration requires a disproportionate effort for the number of people it benefits.
However, accommodating the needs of minorities, whilst sometimes costly and time consuming, does not usually cause harm to another group.
Where the rights and needs of two different groups are in direct conflict with each other and the requirements of one group cannot be satisfied without disregarding the requirements of the other group, it is reasonable to adopt a utilitarian approach, and opt for whichever solution works for the greatest number of people.
If, at a generous estimate, trans women represent 0.5% of the population and women represent roughly 50% of the population, there are about a hundred times as many women as trans women.
This would indicate that the focus should be on the impact on people with female bodies of allowing people with male bodies into female only spaces, rather than the impact on people with male bodies and female brains of being excluded from female only spaces.
Only in circumstances where the impact on the female 50% of the population of allowing people with male bodies into female only spaces was negligible, and the impact on the trans identifying male 0.5% of the population of denying them access to female only spaces was catastrophic, should society ever contemplate prioritising the 0.5% over the 50%.
Because to do so would be to take the position that one male bodied person is more important than a hundred female bodied people.
As far as I am aware, even the Taliban don't have that as an official policy.