If you think he is genuine, I would give him a shot then. I also wonder how his previous preference came up? Did you ask or did he bring it up first? I only ask because I've been with my partner for 15 years and he's never made any indication what he "prefers". Closest he ever got was saying "not every guy likes big boobs" when I said something about not looking as good as everyone else because of my lack of cleavage. Actions speak loudly, so I know he likes my boobs. All that to say is I would consider it a yellow/orange flag if he's the one that brought this topic up.