i think the brother explains it as they get scared instictively so a defence mechanism kicks in which is the pleasure hormone. I like to think of it as a feinting goat instinct. He's also mostly confused at any given time so i think it's a bit of both in the end ╮( ̄▽ ̄)╭
Maybe I'm just that stupid but is he actually frightened for his life when they fk or is he just incapable of labeling horniness correctly