The dangers of N=1 studies. I've met people for whom it was almost entirely a question of body image, and people for whom it was almost entirely a question of social perception - if they were exiled to a desert island forever, they would feel very little gender dysphoria, the problems start when people start saying "You're such a beautiful girl!" instead of "You're such a strong boy!".

Transpeople with that "I should have this disability" disorder confirm that the dysphoria induced by extra limbs or senses are similar to the dysphoria induced by having a wrongly sexed body, so you're right.