One factor that might make Pythag less consistently predictive in ATG than in MLB is the hypercharged offenses in ATG. Even in an 80M league, most team offenses are way more potent than in actual major league baseball. And at higher caps, the offenses get even more potent And, the more runs that teams score in a league, the more likely they are to generate 20-2 outcomes that can really throw off pythag predictions.
I have a 175M team in a Godfather league that currently has a +82 run differential and a losing 53-58 record. My Exp.W/L for this team is 62-49, so I'm 9 games behind expectations. I'm 11-15 in 1 run games, so that's part of it.
Perhaps more significantly, my team has won games several games by huge margins, including scores of 17-7, 11-0, 22-4, 16-6, 16-2, 13-1, 12-2, 15-3, etc, etc. Meanwhile, my largest run differential in a loss appears to be 8 runs, and the losing differentials for my team go down rapidly from there.
Obviously, I've had some bad luck in terms of winning the blowouts with garbage runs while I've losing the close ones. More significantly, though, this league's ERA is 5.72--an ERA you would never see in actual baseball.
So, when lots of runs are scored, there are more blowouts. And I would suggest that the more common blowouts are, the more likely it is that pythag will not be consistently predictive.
I'm still hoping this team will turn it around, and there's enough time that they could make up the 5 games they're currently trailing the division leader by. In a couple of weeks, we'll know:
https://365.strat-o-matic.com/team/1729588