Matchmaker games adjust real rating of global while breaking rules of trueskill, causing rating inflation in global

There's a popular perspective that global rating has inflated in the past few years. What used to be the near-top players at 2k rating is now 2.4k and higher, with some reaching around 2.7k in mostly legitimate gameplay.

I hypothesized that the matchmaker -> global rating adjustment could be the source of that influx of rating for global.

From my limited understand of the code, here's what I understood looking at it:
The game rating adjuster breaks trueskill in 2 ways:
- It does not reduce the global rating of the opponent if they lose
- It only allows rating to move up

https://github.com/FAForever/server/blob/736b238067ceebb82c7238ad881636b998c7bb02/server/rating_service/game_rater.py#L74-L112

As I understand in this function, the rating adjuster adjusts the real global rating history of the player.

https://github.com/FAForever/server/blob/736b238067ceebb82c7238ad881636b998c7bb02/server/rating_service/rating_service.py#L153-L198

For a trueskill-compatible system, I would've expected something like adjusting only a secondary global visual rating. The visual rating would be given to clients to protect new players from player-led rating discrimination.

Team balance functions in matchmaker and custom game lobby should ideally be given the real rating, with any UI elements using visual rating, but if that's too difficult then just balancing by visual rating is possible too, since trueskill will calculate the results of such imbalanced non-50/50 games correctly as particularly expected/unexpected outcomes.
In theory there could be problems of players feeling like the game is creating unfair lobbies, but I think that visual rating being used for balance should be ok as it is under the reasonable assumption that matchmaker skill transfers to real games, and if real rating is used for balance then it should adjust close enough to visual rating to create fair lobbies within 10 games.