In regards to the first sentence or the second? If the former, then I think yes. I shoot CO now, we don't have GMs in it locally, only Ms, but it is M class guys who win matches, not me with my A. Incidentally, higher % Ms win, not barely there paper Ms. When I shot Production, it was again GM or high Ms who were winning.
Here is a link to the Limited Nats results. Choosing Limited simply because it is a long established and popular division. Pretty telling as far as what letters are mostly seen at the top vs middle vs bottom.
https://practiscore.com/results/new/93422?q_division=2