Transition (and by extension gender) is something deeply personal that shouldn't be gated by physical characteristics, including brain development.

Hope that helps!

It's often associated with TERFs, but it is VERY common within transgender communities themselves. There's notion that certain gender identities are valid and others are not (especially being male/female), and there's also the notion that diagnosable medical issues are required to be truly transgender.

In this conversation, if you're AMAB, and have a male brain, and claim to have transitioned to being non-binary a gender essentialist might go "aha! Science proves they are nothing but a transtrender and a man" A constructionist would say "aha - the fact they have a male brain yet expresses a non-male gender identity proves they're a truly unique and special transgender person".

It seems like an easy way to be on the "Right side of history" to reject gender essentialism, since you end up never calling a transgender person invalid. There is a dark side to rejecting essentialism, which is if gender ISN'T essential, than logically it should be possible to change people's gender identity to a "better" one. Which can result in things like Joan/John https://en.wikipedia.org/wiki/David_Reimer.