I think Roger meant it as 80% of what Roger knows, doesn't work in MMA. This can be misleading because Roger must have a wealth of knowledge and 20% of his knowledge, is a ton. So the 20% that does work, is IMO more effective than whatever percentage of Judo, Sambo, Catch Wrestling etc... (excluding TPJJ because I see it as a flavor of BJJ) that works in MMA. When martial artists only trained one style back in the early ufc days, it was GJJ on top and not any sambo, judo, or catch wrestling guys. So that alone should be proof of BJJ's dominance as the superior grappling style. Even in No-Gi grappling, BJJ guys rule the world championships year after year. Of course you always have your exceptions though.