Fighter generation used to be pretty universal that everyone except russian agrees that modern fighter jets like Su-27,F-15, and eurofighter are third gen and stealth fighter being fourth gen. Back then Lockheed Martin's promotion slogan for F-22 was still something like "FOURTH gen with FOUR S". But after T-50 appeared (russian 5th gen) these glorified salesmen just couldn't stand the word game of being one gen behind so they came with the good idea of reinventing fighter generation classification and brain fucking everyone.This doesn’t even make any sense. The Chinese definition for fighter generation, or at least the one before 2020, is one level below that of the US one so that Chinese 4th gen is the same as US fifth gen. For his argument to work China has to claim that the J20 is a 3.5th gen fighter, which has not happened ever.