I think DiscGolfScene used to have a rule about the distance between B-tiers and higher....but I believe that no longer exists.
The reason (as I recall) was that it was difficult to get people to sign up for tournaments, so they limited how close they could be so one didn't take players away from the other. But that's not really an issue anymore - now there's so many people trying to get into tournaments that you could have one right next to the other and probably fill both.
(I had a friend who had to change the date of a tournament because it was too close, mileage-wise, to another one....but that was before Covid and the huge increase in players).