Like blackmesa said, no they don't need to redownload the map, only a small file and would likely never notice anyways.
I guess the logic here could be, what could it hurt?
If 1 player reads it and adheres by the rules because of it, and that player enjoys, has a good time, becomes a members, invites friends, ect ect ect, then I think it'd all be worth it.
It's not like doing so would be a huge undertaking or anything.