The only thing I noticed is that you lose more SR when you Q up for the next game and happen to lose that one as well. That is why I never leave after the 2 mins are up and am always the only one left on my team and leave when the game says defeat.
I haven’t left after the 2 mins were up for a very long time so I do not know if you actually lose more then. If you stay until the end you lose the same amount as usual.