I don't understand. If there's no rule that defines how Int 5 has to be presented, then how is there a disconnect between roleplaying and mechanics if somebody interprets it in a surprising way?
I get that in your opinion a 5 Int has a certain meaning, but that makes the disconnect between your expectations and the player's, not between the roleplaying and the rules.
In other words, maybe it just bugs you, and you don't want that at your table because it interferes with your conception of how things should be. That's fine. But I think you're interpreting your own opinion as objective, as something that's defined by the game.