I also think that the fact that only AEROBIC bacteria colonizes the bioballs, and detritus or no, that stops the cycle at NO3, period. LR has a certain amount of ANAEROBIC bacteria deep within the rock, which DOES process NO3. To be honest, the BEST thing is to keep the NH3 OUT of the nitrogen cycle in the first place, which is where skimmers, macro, etc. comes in.
Macro algae will feed on NO3 if that's all there is, but it will use NH3 first, so with macro, it's a win-win situation. Nutrient export is accomplished via pruning the macro.
As Henry said, so far, no single part of a system is perfect, which is why we still need WC's...how much and how often depends upon the efficiency of the system in question.