The game sets it up for the player to be advised to consider the meaning of these things, but to ultimately decide for themselves how it informs their character's appearance and personality. For a particular portrayal to violate the social contract, as you say here, it must exist as an agreement at the level of table rules. People should be held to their agreements, but the game rules don't actually say what the player must do here other than take what it says into account when deciding. A group that lacks this table rule has no issue with a social contract violation when a player decides to portray the character as Sherlock Holmes while having an Int 5, for example.