No they are incorrect.

Despite what radical feminists will tell you, yes you can tell someone's sex from their brain about 95% plus of the time. The tricky brains belong to homosexuals, who are intermediate to both sexes. There's not much difference between a gay man and gay woman.

This matters, because children with gender dysphoria are about 90% gay as adults.

So when the MRI studies were done on people with gender dysphoria in childhood, they were picking up the 'intersexness' of their gay brains, not anything to do with being trans.

A couple of researchers specifically corrected for this, comparing gay trans to gay cis, and heterosexual trans to heterosexual cis.

Turns out that the trans brains were normally sexually developed. What did show up as different was a connective tissue bundle called the IFOF, which was abnormal but only in transwomen, and even then some of them still came into the normal range, mainly in the hetero trans.

The IFOF gets implicated in a lot of mental health conditions, including OCD and anxiety and body image issues.

I'll paste the papers below

New MRI Studies Support the Blanchard Typology of Male-to-Female Transsexualism

T]he brains of both homosexual and heterosexual male-to-female transsexuals probably differ from the brains of typical heterosexual men, but in different ways. In homosexual male-to-female transsexuals, the difference does involve sex-dimorphic structures, and the nature of the difference is a shift in the female-typical direction. If there is any neuroanatomic intersexuality, it is in the homosexual group. In heterosexual male-to-female transsexuals, the difference may not involve sex-dimorphic structures at all, and the nature of the structural difference is not necessarily along the male–female dimension.

As Savic and Arver themselves emphasized, “Contrary to the primary hypothesis, no sex-atypical features with signs of ‘feminization’ were detected in the transsexual group….The present study does not support the dogma that [male-to-female transsexuals] have atypical sex dimorphism in the brain”

Savic also did another paper:

Structural connections in the brain in relation to gender identity and sexual orientation

After controlling for sexual orientation, the transgender groups showed sex-typical FA-values. The only exception was the right inferior fronto-occipital tract, connecting parietal and frontal brain areas that mediate own body perception.

It's also a fact the overwhelming majority of trans never had childhood GD.

A Critique of the Brain-Sex Theory ofTranssexualism 2007

In 2002, the brain-sex theory of transsexualism was seriously challenged by someunexpected findings published by Chung, De Vries, and Swaab. They observed thatsignificant sexual dimorphism in BSTc volume and neuron number does not develop inhumans until adulthood. Most MtF transsexuals, however, report that their feelings ofgender dysphoria began in early childhood. The mostly likely explanation: The Zhou/Kruijver findings reflect the effects of feminizing and masculinizing hormone therapy*

What is odd is that there's psychiatric issue called BIID, where people believe they should be missing a body part or disabled... 19% of them are also transgender, and this is from a time where the rate of trans was one in several thousand in the general population.