I remember reading somewhere that there's a higher incidence of PCOS (resulting in higher than normal T) in FtMs than in the cis female population... Not sure how accurate that is or whether that has something to do with why we're FtM, but there's that.
I have PCOS: elevated T levels, irregular period, a bit too hairy compared to other females, with facial hair that even years of laser hasn't gotten rid of, always had a decent amount of muscle even when I never worked out.. But then again, my dad has a lot of muscle even though he was never into weight lifting, he sometimes talks about how his friends think he lifts.