ask you, if the place is not large, if you smother it with 20 photographers, then how?
say, lower peirce, if have 10 photographers scrambling around the rocks, i guarantee you only one guy will get a passable shot, and that is the one without any other photographers in his picture, and if all use UWA there will only be one guy getting a passable shot.
or you have to take turns. sad to say, you won't know which moment has the best light, i cannot say that i am kind enough to sit back and take turns and not feel anything if the best light happens when it is the other guy's turn.
i think 5 for a large area is the maximum to make sure that you don't get in each other's way.
unless you all want to stand far far back around the same area and provide slightly different angles of the same thing... which is what happens a lot nowadays.
one of my friends complained to me that it wasn't bad enough that travel/landscapes was smothered with singapore photos, but it got worse with all these group outings, because he would click on the thread, and end up seeing 8000 pictures that looked like different wb used, but 100% same composition, taken at the same time.
it is like taking a model, mass photoshoot versus one-on-one proper collaboration, which do you think is better? your subject is the landscape, over-crowding your subject is not going to give you good results overall.