How about some actual facts in this discussion or would that ruin it?
There's no evidence that players play better or worse in tournaments playing in groups with a higher or lower ratings average than themselves in terms of their actual round ratings. Certainly if reverse discmosis was real, then Climo would have been pulled down from the top long before winning all of those titles in a row. Not sure he has ever played in a group with a higher average rating than his since the early 90s.
There are more newer, lower rated players coming on the competition scene. It would only make sense that there are more examples of players improving than declining regardless of the reasons, and they are statistically more likely to be playing with higher rated players in their groups. So the correlation is going to be there, but claiming there's a cause and effect relationship is a stretch.
For players to get better, they need to learn new skills and practice. It would make sense that they can learn some new things from better players in a tournament or league in addition to casual rounds. But that new knowledge may mean nothing during the round itself, just the next time they play.