I guess I can see why it doesn't work for everyone, but it was just the one time, and as I said, it was an exceptional scene and the extra "nons" were for emphasis. Sure, if you take it out of context, it's just dumb. Most of the Bill and Ted movies are dumb humor.
To me, it's kinda like Harold and Kumar. They have this thing where they emphasize something by negating its opposite. Kumar will say "Man, I'm high" and Harold will agree "I'm not low". Kumar will say "You're worthless" and Harold will agree "I'm not worthwhile". And of course the most famous one, Katie Holmes' tits in "The Gift". How were they? Well, think of The Holocaust; they are the exact opposite. The Holocaust is something truly horrible; Katie Holmes' tits are the exact opposite of truly horrible.
I like stuff like that because it's the kind of quirky verbal banter that real buddies develop over time, so including them in buddy movies adds a degree of realism. My buddies and I from back home have a few of these that make us laugh, and everyone else just groans or is confused. Of course, to work in a movie, it also has to be funny and make sense. For me, it (even number of "nons" = bad, odd number = good) does both, so it works.