The "200 points difference means 25% chance to win" breaks down at the highest levels. It works fine near the middle of the bell curve -- i.e. 800-2000 Elo -- but once you get to 2200 Elo you are talking about the >99th percentile. For example, I don't know of a single 2400 player who can score an average of 0.25 against 2600 players.

Even at my own mediocre level of 1800, I definitely do not score 0.25 against 2000 rated players. More like 0.1 if I'm feeling sharp.