Let me see if I understand you: you are implying that when coding Catan for BGA you think the progammer took the extra steps to:
1. Check the ratings of the players in the game (which assumes the programming of BGA took the extra step to make that information accessible to the code of the game).
2. Figure out which player has a higher rating
3. Determine which dice rolls would be most beneficial to that player at the time. (Giving them 2 brick when they have 5 is less useful than giving them the 1 wood they really need right now)
4. Program the game to actively change the dice rolls to better help the player with the higher ranking
5. Determine how often the game should change the dice rolls in this fashion in order to aid the higher ranked player to be beneficial but not obvious.
6. This is all done because.... Reasons?
And you think this is more likely the case than the higher ranked player doing better because they are better at the game?
This is an excellent example as to why there aren't more elaborate reporting tools. If someone is going to legitimately imply that the game itself is cheating on behalf of their opponent, what is the likelihood of someone accusing their opponents of collusion when no collusion was actually happening? How do you prevent someone salty from losing from just lying and saying their opponents were cheating when no such thing was actually happening?
Sure, if the same 3 players get reported frequently by different players I could see the argument for having mods look into it, but the threshold needs to be significantly high enough that I can't just grab a handful of buddies and get you labeled a cheater just because you beat me in a game.
The end result looks the same on your end: you report/red thumb, don't get matched with the player again, and have no idea if any action takes place.
My proposal: introduce a "elevator close for button" reporting method (99.9% of the time the elevator close door button does nothing, but it lets people think they're actively doing something), a form where players can "report cheating" after a game.
They can type whatever they want, once they click submit the are told "thank you for your report. If enough players report suspected cheaters our mods will look into their play logs". The user they 'reported' is hidden from them the same as a red thumb, and the report itself is thrown away. They can feel like they're "doing something" while the only practical course of action takes place: they will no longer be matched with that player in the future.