What happens if someone admits defeat before having the proper result or leaving the game without admiting defeat? That can change the magnitude of the victory, and could result that on 3rd game the player who should choose wheter attack or defend cannot do it.
I think that this should be considered as epic victory, but of course we must trust in the honourability of the players to avoid unit spaming, running all the battlefield when the game is lost.
There is no rule saying anything about admitting defeat but from my experience the best solution is to not admit defeats. But if it's gonna be introduced then no sooner than from 3rd Round on - we will let players know if it happens.