No, obviously he's progressed enormously. He ran the game out, but looked stuffed a few times. I'm not having a crack at him either, just giving my two cents as to why he might still be catching up with some others on fitness despite the two years you mention.
Also up to this point, Collingwood only regarded Cox as an experimental project and probably weren't willing to invest too much resources into his development. Now that he is starting to show some promise, hopefully Collingwood will take his development more seriously.