The cup restrictions involve legendaries, levels, if pokemon evolve, their height and size, items, duplicate pokemon, etc.
I agree that using other methods to obtain a bunch of rare candies IS cheating, but I don't define it AS cheating. A quick estimate I make tells me it'll take at LEAST 15-20 clearings of the elite four, with trade bonus and lucky egg/exp share to get to level 100, maybe more maybe less depending on what pokemon. If a clear takes 5-10 minutes, you're looking at 2-4 hours roughly for EACH pokemon. If I intend to legitimately get my pokemon to 100, after breedings, EVs, movesets etc, I fail to see why I should spend that ADDED time on top of doing all that to get it to 100. I will anyways, so to save myself from repetition, I use a method to level them that's in the game, but use "unfavourable" methods of obtaining the items. The pokemon are still legit.







