The AI personalities only apply to the main characters. What I meant was that if you only set an AI personality for one character because you were planing on using the other for most conversations, if you happened to be controlling the character with the AI personality, then you would have to make choices for both. Since you set a personality for both of them, though, that isn't the case.
Are the dual dialogue that do not work just between party members, with NPCs or both?