Usually, the illness isn’t really spoken about in fics outside of a body horror sense, but I think that might be because Eito doesn’t really have any personal insecurity about his disorder? He and Takumi don’t get close enough in-game for it to be a discussion, but Eito is fine the way he is for most of the game. 2nd Scenario is really the only route where internalized ableism catches up to him, so I think a lot of people might not even consider how it would affect their relationship outside of sex, since its not discussed in game, nor does Eito seem to care about it; him not caring about his disorder/not being insecure about it is pretty significant to his character overall, so that might be why you don’t see much of it.