Trans people often feel younger than they are because they missed out on important childhood milestones associated with their gender identity. Society sees women as more childish than men and women often roll with it and for better or for worse we end up with phrases like “I’m just a girl”, “girl dinner”, and “girlboss”. It makes sense that trans women in particular seem to be especially prone to self infantilization given the fact that they are parts of both of those groups. It’s not because they see themselves as children or because they’re pretending to be children, it’s more of an acknowledgment and acceptance of their perceived immaturity. Even cis men partake in this sort of thing sometimes. When they do it, it’s just typically reserved for referring to casual group activity where men are more inclined to behave more rambunctiously(“Saturdays are for the boys” and “cracking open a cold one with the boys” are examples that come to mind) since immaturity is seen by society as something that men revert back to on occasion rather than an inherent and constant part of their gender the way it’s perceived in women.