Yep, the "math" in many leagues is faulty. Some assume if you play a safe you are an advanced player so it counts towards your score to go up in level. That is absolutely false, like assuming if you have an expensive cue you are a good player. A lvl 3 can play safe if they are getting coached, or can be just taking lessons from someone that explained what a safe is and when to play one.
Innings per game is the same thing, yes a bad player can take 4 turns at the table to win a game. But so can a pro if the layout is bad or there is safety play that was done.
In fact those exact things are what causes sandbagging to be so effective, a good player can just bat around the balls, play "misses" that are really safes, and still win vs a weak player easily since they won't be leaving any open shots. Sure they take 4 turns at the table each game but that does not matter much.
USAPL I think has the best scoring, you don't count anything except balls made and win/loss of the game. Does not matter if you missed 20 shots a rack, if you made 5 balls, you made 5 balls, if you won the rack, you won the rack.