Sorry for the long title, couldn't think how to phrase it concisely.
Basically, if you change the game mode from duplicate to unique demigods in the options in the lobby if two players are already duplicate demigods they can stay that way. Say if I was 1 v 1 both TB, then put it on unique mode, we'd both still be able to play as TB, and only if you go into the demigod selection screen will it prevent you from selecting TB as he's already taken by someone else. Not sure if this is intentional\already picked up but left that way on purpose (I could see how it could lead to problems with 4 or more players as there are only 3 unique demigods atm), so I though't I'd post it in case.