Centuries of heterosexuality being the only normal option didn't stop people from being gay or transgender, it only made them stay in the closet. Transgender is not suddenly so "cool" that kids are going to want to change their idenity just so they can be a part of the group.It is happening, how much it is is definitely up for debate though. I believe it as Abigail Shier who presented the data on the ratio of female to male transitions vs male to female in young adults. Heavily weighted to female to male transitions and, not shockingly, in small social circles of girls.
She goes into it pretty well on Rogan's podcast. I'll link it, even though nobody will take the time to listen to it.