I mean, I'd argue casuals benefit from this too. Coming from a casual player myself, I like battling my friends but sometimes things happen and we need to cut it short. Like we accidentally accepted the duel when one of us hasn't been to the pokecenter yet. Would be real nice to be able to quit the fight and redo it in an easy manner.
Or if you accidentally accept a duel request from a player super uber more powerful than you. It'd be nice for casuals to be able to leave the battle and move on with their lives instead of force disconnect or sit there and wait for their one-way trip to the pokemon center to finish.