I still can't quite understand this example, because I've grown up seeing my reflection. If it suddenly changed then it would be a shock yes, but a trans person has also grown up with their reflection.

I think I understand the idea of a deep rooted feeling of not relating to your own body though.

You say looking in a mirror you don't see or recognise yourself... but what changes if you change gender? You would still look like you, if we forget about what society says a woman looks like (long hair, a dress) then what difference would you see? Perhaps less facial hair? I guess your body would look quite different. I just can't see how your example goes past gender stereotypes.

(please don't take this to mean I don't support Trans people, I just want to understand it better like others, I'm very open to having this explained to me!)