@Admmi
I haven’t read this (but I’m about to)
It doesn’t seem impossible to fall in love with someone of one gender at 14 (looking at the description here), develop in the opposite direction of that person, then to fall in love with someone else at a later time.
If anything, having so many people changing genders might make it so that there are more same-sex relationships.
(I’m assuming that once you’ve changed sex, it’s locked in)
But hey, maybe I should just read it already, instead of assuming everything.