This has only been proven true in the Kepler vs early GCN generation, Fiji generation aged badly for AMD, so much that FuryX is behaving like an RX 580/590 in a great deal of titles in the past two years.
Its true for Paxwell too, just not quite as bad as Kepler. I wouldn't be surprised if it happens again with Turing. Isnt FuryX the only AMD GPU that hasnt aged significantly better than its competition since the introduction of GCN?