If that were the case realistic patterns would produce better than standard nymphs. I am not aware of this being the case, but I could be wrong. I suppose if you can calculate the exact body density of each individual nymph. Not to mention species. And, get it/them to tumble exactly as a natural would while attached to your tippet, you would be on to something. I do not see many realistic patterns winning trout competitions. I do see a lot of generic attractors winning though. There comes a point when the fisherman is caught by the pattern and not the trout.