It might be! I don't think it's unheard-of that the prince left hints to the door riddles. He's not mean-spirited, even if his doors do eat a lot of people.

[She's amused, though, and pets his hair as she teases: ]

But that sort of answer is why it's good you are more the type of the handsome prince, and not the clever girl. The door wanted "a soul you can hold", so she took off her shoe and she fed it to the door.