The most RV's packed into a small area we've ever seen was Fort Peck in Montana this summer, they were practically parked hubcap to hubcap, scores of them in parking lots and these were not just parked there. This despite signs all over the place forbidding the practice. No enforcement at all. However our official CG was well managed and excellent as the other cg seemed to be as well.
Jug Hollow in Flaming Gorge had scores of RVs but they were all placed apart from each other. We could just see the roof of our nearest neighbor. That area is so large it can accommodate a lot of people and still give them separation.