The inquiries into brain structure you cite already assume that a person can have the brain of one sex and all the other body parts of the opposite sex. The people doing those studies already have singled out the brain and brain cells alone for special status that none of the rest of the body gets. In their view, the brain and its cells the are the organ and cells stand out as entirely separate and different to all the rest of the body and all the other kinds of cells. In fact, they see the brain and its cells as opposite to all the other non-brain body parts and all the other non-brain cells. Why and how would this be?

Also: if there were brain differences showing that some people are "born in the wrong body," then they would have to be present at birth. Gender vendors say that infants are capable of using nonverbal/preverbal methods of communication to tell adults they were born in the wrong body, and people who were indoctrinated into genderist gibberish woo from infancy claim they always knew from their earliest memory that they had the brain of one sex and the body of another. Jazz Jennings, for example, says he was born with "a girl brain in a boy body" and to back this up Jazz and his mum frequently claim that from the moment Jazz first learnt to string words together as a tot he asked his mum, "when will the (good) fairy come to change my penis into a vagina?"

The way to test the validity of the "born in the wrong body" hypothesis would be to do brain scans on a large number of human neonates prior to when the "mini puberty of infancy" begins at circa 4 weeks after birth in order to establish once and for all

a) if nearly all infants really are born with brains that have observable sex-linked structural differences that make it possible to tell male baby brains from female baby brains and thus validate the claim that we're all born with either a boy brain or a girl brain - and if this is the case, where in the brain these differences are, how they can be characterized, and just how pronounced they are;

b) if there really is a small subset of neonates of each of the two sexes who have brains that are not just distinctly different from the brains that nearly all neonates of their own sex have, but which are identical to the brains of neonates of the opposite sex. Aka "trans brains."

Since brain scans don't cause any harm, I imagine doing a large scale study involving scans on neonates could be justified ethically. In fact, since proving or disproving beliefs that we all have marked different brains from birth based on our sex would be of great benefit to so many people, I wonder why those whose belief in trandsgenderism rests on the belief that all humans are born with sexed/gendered brains aren't clamoring for this research to be done.

Given how much medical care and interventions people like Jazz Jennings have had in their young lives starting from early ages, I'm surprised that kids diagnosed with gender dysphoria in early childhood don't all get brain scans at the time of diagnosis and haven't been given brain scans at regular intervals ever since.

If Jazz Jennings, say, really was born with a "girl brain in a boy body," it seems odd that no effort has been made to learn and document what exactly Jazz's "girl brain" looked like when Jazz was 2, 3, 4 and so on - and to find out in what ways, if any, Jazz's "girl brain" changed in the months and years after Jazz started on GnRH agonists to block development when Jazz was 11, and started taking estrogen later that same year to begin "feminizing" Jazz's outward appearance. Also, I'd think Jazz, Jazz's horrible parents, Jazz's doctors and Jazz all would be interested in finding out if and how Jazz's "girl brain" changed following genital surgeries. From the outside appearance of Jazz's body, Jazz doesn't look like Jazz is doing very well these days. But maybe scans of Jazz's brain tell a difference story?