I do mean person born a male that wants to become female. Anti-trans people often make points that trans people are just forced into being trans by the trans-mafia (or whatever term they use) aka social pressure. A brain scan indicating a female brain would counter that. But as I said, they'd probably find other excuses "it's a mental disease that can be treated" and so on and so forth.
I was saying it would be less interesting if it scanned say a female-to-male trans person and returned a result of female (correctly guessing the sex but not the gender), than if it had returned a result of male (that is correctly guessing the gender but not the sex).
That would embolden the anti-trans crowd.
Science is ongoing though, so who knows what the results will be.