I_love_anime , you are talking about a teenage boy who is able to
fake impotence. Which makes me think that you can only be a girl who knows very little about teen boys.
You clearly have no clue what you're talking about.
Even grown men need some serious concentration to suppress an erection and in some situations every one of them would eventually fail, unless they have a real ED problem.
For a teenage boy it would be physiologically impossible to successfully fake and lie about it in all the situations described in the game. About as impossible as stopping his heart or holding his breath for 20 minutes at will.
Getting an erection is an almost uncontrollable reflex, especially for a teenage boy. I still remember the hell I went through as a teen, getting these random boners now and then, even without any real reason at all.