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This does backup my assertion that, *if* innings carried the weight some claim, we wouldn't see the skill disparity gap between same-rated players from different regions. Furthermore, that SLs are competition-based, contingent mostly on W/L against other players within respective league.
Though the AI's response is fuzzy and doesn't say much, "innings played do not directly affect" is at odds with any discussion I've seen over the last few decades. That old document a few mentioned described a system for which inning counts were indeed a key ingredient, like the tomatoes in Grandma's tomato sauce.
I believe the system described there computed, for a player's last 20 matches, the average number of non-safety innings per game win, I think using only the best 10 in the average. (call this NSI/win). Players were then binned into SL groups where, for example SL 6 is NSI/win between 2.0 and 3.0.
It caps NSI/win contributions for new match wins using a table of "applied scores" that depend on SL and also on overall match win%. For example if you are a SL6 who wins 50% of your matches, you might be expected to be a mid-level 6 and have NSI/win in the mid-6 range, around 2.5. The cap prevents you from both winning a match and also recording an NSI/win larger than this expectation. An SL6 who wins 80% of matches--presumably a strong SL6 or an SL7 in disguise-- has a stricter cap, like 2.2. And an SL6 who wins only 20% of matches might be allowed an NSI/win up to 2.8 for his new match wins.
So long as the level of competition is not wildly different from league to league, the inning count idea should lead to skill levels that are fairly independent of region. At the next level of scrutiny, though, a player of a given skill (let's say Fargo Rating of 500) will have a lower NSI/win in a league filled with 600s than he would have in a league filled with 300s. This is because against weak opponents there are on average more opponent balls on table for your win attempt at any given inning number.
Maybe that was/is the gist of it. Maybe not. Either way it seems like a pretty clever approach, imo.
I would not have expected the idea that inning counts play a primary role to be secret or controversial.