I'm not sure I fully understand why MAE is that big there (~0.35). Is it a difference between theoretical (based on rating difference of players) expected score and actual score averaged over many games? If score is in range 0-1, then MAE=0.35 seems a huge to me. I get it, that there is some deviation from theoretical prediction, but if I understood correctly it happens for larger ratings difference, but I guess more games should be played between players of similar strength.