[Al Skierkiewicz]

While it would seem that this is an RF interference issue, that is not all. It is part of the "leveling the playing field" issue. Any item that could give a team an advantage over other teams that is not specifically allowed in the rules, is likewise banned. That is why you can't use a bigger battery or motors not listed.
And by the way, you don't have to be on the same frequency to produce interference. Ask me about this sometime. It is a very complex subject.