I wouldn’t say that about sexual orientation because unlike gender, sexual orientation can’t be changed, as far as I know.
Philosophically there are two schools of thought. Either gender is arbitrary (1), or gender is not arbitrary (2). If the former, then people’s gender is entirely determined by their preferences, and it can change. If the latter, then there are factors outside of one’s preferences that determine their gender, which cannot change based on personal reflection.
Most people believe that gender can change (position 1). Ergo, my phrasing. Trans men are men. (And gender can change based on your preferences). I’ll freely admit I phrased my reply in a way intended to confuse and annoy you.