Are you saying that being trans is biologically rooted?

That a person who is trans is born that way, with some innate/instinctive ability to sense what gender they are?

If so... how could we have a biologically rooted sense of a social construct? How can your biology tell you that you "are" a thing that only exists within the context of certain cultural norms?

How could humans evolve an instinct for something - like style of dress or makeup or other social conventions - which only exists in a specific culture, for a specific and brief period of time?

If you are not saying that it's biologically rooted, then where does this 'sense of self' come from?

I'm not arguing that Trans people 'choose' their sense of self: but I do think that this sense of self is formed by their learning/absorbing cultural norms. The sense of self will largely be subconscious, not actively chosen. But since cultural norms are an overly simplified understanding of reality, we should encourage the expanding of that understanding, rather than a reliance on it/acceptance of it.