Because I think it's correct to say "some trans people are genuine".
Even if there are different pathways, that doesn't mean it can't be genuine identity for them.
As I was recently saying with political lesbianism, I wouldn't rule out the possibility that if you embrace an ideology, it could genuinely turn off one side of your sexuality in select cases. So for a minority of people perhaps.
So they could end up as "exclusively same sex attracted to women" because of their ideological commitment.
I don't think multiple pathways to lesbianism would mean that lesbianism isn't a real thing. Even if political lesbians may have a less stable identity and may go back to men. Like maybe when the ideological commitment weakens.
And perhaps there are multiple pathways for trans, and some should be treated in a medically different way, or considered as less stable identities where medical transition is less justified.