Well, if it is just a preference, how to explain the pain and utter wrongness when the body does not fit to the expectations of the self, if the self is reflective of the soul. I mean - I did not really just prefer being a girl when I was little or in puberty, I had that deep longing for a female body and did not really make it into adulthood without eventuelly doing what I could to get it. Puberty was so painful - I guess something inside me was just very clear about how my body and gender should be - if not the soul, what then?
Maybe it is a preferrence , but the expectation still is there that the preferrence will be met and that is fixed then? I dont know.
I asked some people about being born again and got two different replies. The question was, if you had the chance to be reborn, what would you wish for. Some people said they would want a female body fitting to their female self. Others basically said that their most wish was to be born cis - no matter what body they would get as long as their self would then fit to that. I found this interesting that for some, the soul, their self would be fixed and forever demand a female body, while for others their self was not that fixed, their souls were according to their thoughts not gendered (or gendered male maybe?) and they just wished for a life without discrepancy.