Urgh... I don't know how I missed this before, but ELO rankings are not used in the Leagues, only in the Ladders. This actually makes sense, because Leagues already have a built-in fairness function in them, because everyone plays everyone else exactly the same number of times, so simply tracking wins and losses is an accurate measurement. ELO is only used in Ladders, because in Ladders players will not end up playing the exact same people, so a different evaluation system is still needed.