By my definition it's meta to do opponent modeling since you are using information outside of the game mechanics. And you're right, for games with high efficie

By my definition it's meta to do opponent modeling since you are using information outside of the game mechanics. And you're right, for games with high efficiency and public knowledge you can often just grind through optimal play. However, for games with hidden information, you can play theoretical optimally, but you can also gain an additional edge if you can properly model your opponent. I'm thinking like in Poker. There's mathematically correct play, but because you play against folks who don't play mathematically correct you could get an extra edge by properly modeling the faults of your opponent you can exploit!