It is cheating. Yes its within the rules and whatever other bureaucracy applies. But any fighter weight cutting big weight is doing it because they want to be bigger then their opponent. And as Joe says, in the context of true martial arts, its cheating. You are trying to cheat. I dont care if its not in a handbook.
Then you get guys, who choose not to cut and are effectively being punished for it. Edgar at LW and Machida at LHW spring to mind. Both forced to cut down because they have compete against the cheating monsters that occupy their divisions.
Great info regards Alves. Hes actually managed to get down to a sustainable 170. That's very impressive.