Well you get the Overwhelming Advantage kicking in which makes hunting the last units pretty easy in the few cases it happens.
On the whole, I'm not sure it will shorten games or not.
Like sometimes, if the game lasts for a long time, lots of people might resign and do something else while waiting for the game end and while not caring to vote or watching the vote. In that case, it probably shortens already precluded games.
On the other hand, if someone is really stubborn and want to play the match out, they will be able to do that. Well the other players already resigned from the game, so why should they vote on the continuation, when they could, you know, go into another game room and try to start another battle in another lobby.
I find it annoying when people resign early just because they lost their lane and don't care about what else is happening on the map and just keeps voting to resign and start a new game. Sometimes games end way to early from that.