He can still be an amab femboy and take hrt to become more feminine without transitioning to become a woman. He does not claim to be trans, just a femboy.
Well sure but… Why? That’s a great way to give a huge blow to your body for fun. Anyway, it’s 4chan so whatever. In any case you are right, I assumed more than was stated.
Does it matter why? Bodily autonomy means bodily autonomy for everyone, regardless of whether you “understand” or or not. If he wants to be a more feminized masc, is it hurting you?
People modify (“deal a huge blow to” in your words) their bodies all the time to fit certain preferences. Be it tattoos, piercings (including earrings), cosmetic surgery or even stuff like body building.
It is not that strange that people want to express themselves with their body.