It's not hard to come up with designs where you effectively cycle types of queues to where the end result is 50/50, but the pathway to get there is psychologically manipulative(win streaks/loss streaks/etc...).

Now, winning a single game of LoL is zero-sum, but you can't say that the ratings themselves are. Without knowing what the actual system is doing, we can't assume that players are losing/winning the same number of ranking points in a game.

Ranking should be more or less stable across even a small number of games unless your skill level actually changes.

Trying to draw parallels with singleplayer content where you can progress regardless of actually getting better is a lost cause.