Understanding transgenderism.

[John 6IX Breezy]

Under your theory, there seems no good reason for transgenderism at all aside from rebellious personalities, which is an absurd explanation.

Right, if gender is just a cultural norm, or construct, then transgender individuals are just another counterculture group. No different than listening to rock music a few decades ago. It makes talk of dysphoria incoherent. And it makes the point of transitioning unintelligeble.

Psychologists have not latched on to such single rigid explanations since the middle of the foregone century. Every behavior is understood to be the result of multivariate interactions. As an example, obesity is highly heritable, somewhere near 70%. But no matter how heritable it is, you will never become obese in a famine. You will also not become obese depending on the diet available to your location.

The presence of regional variation does not imply the absence of heritability or biological contributions. Environments, including cultural ones, will always magnify biological differences, that's Evolution 101.