A non-dysphoric person who medically transitions will suddenly experience immense body dysphoria. They may well be unable to return to their previous life wherein they were their birth sex. Read up about detransitioners. Their existence is undeniable, and I'm sure as hell that we'll see a slew of them in the near future.
There are people who want to be LGBT, non-white etc in order to feel oppressed and thereby fit in with the stereotypical "liberal university student". I know this because I used to be one of them. I used to think it would be really cool to be LGBT. Then I realised that I'm trans, and I wish nothing more than not to be. Sadly, I can't because that's not how gender dysphoria works. You can also research transtrenders, of which there are many.