@peemee That's possible--he switched to Android and likely didn't bother with some of the details--but I've got it set up on a new Apple ID, so I would think that the only iCloud account would be associated with the new ID.
I'm guessing that he may have left his SIM in the phone while he was wiping it, and that's why the number remains. I'm running it without a SIM at the moment, so there's nothing to override the phone number info.