You are mistaken. The revised description for the 1201-1400 tournament states the policy that has always been in effect. It appears that erik has not added this to the other tournament descriptions.
http://www.chess.com/tournament/2nd-chesscom-tournament-1201-1400
"Players who's ratings move beyond the rating range of this tournament will be automatically moved to the correct tournament section when the event begins."
For a member-created tournament others have stated they were automatically removed.
If I'm not mistaken I believe that its possible to join tournaments with a certain range of ratings regardless of your own rating. This means that, for example, a 1800 rated played could potentially join a 1200-1400 rated tournament and win every single game. Obviously that player's rating won't increase by that much but I think it lowers the chances of the players that are playing within the range.
Of course there may be a 1450 rated player joining the same tournament but ratings tend to fluctuate...
Is there a way to ensure that no players with a rating higher than a certain amount over the range could join? If not I think this should be an option for those that host tournaments.
Btw I'm speaking about chess.com tournaments of course...
Let me know what you think...