Might be mistaken, but since top shooters are sponsored one way or another (guns, ammo, clothing, travel, match fees...) they would likely prefer not entering a competition that has the following potential downsides:
- strange & unspecified guns & ammo (these guys/gals are hyper-trained on the bio-mechanics of their own gear, including gun specific holsters).
- competition has no track record w.r.t. rules interpretation and officiating (too easy to inadvertently commit faults, FTDRs or whatever).
- risk of losing to an unknown, non-ranked shooter (loss of prestige, embarrassment to sponsor).
The downsides outweigh the upsides.
They'll probably miss out on a lot of fun though.