I would kinda expect him to not do poorly at all, and instead easily deal with it because of happening to know exactly the weaknesses in his normal fighting (patterns, gaps and unguarded points, and so on and so forth). So it was odd to see him pushed back that much tbh.
But I suppose having a 500ms delay (that's half a second) between trying to do a move, and it actually moving, does make it understandable he's failing. That is truly the kind of delay that is only viable in any type of fight if you already know precisely how everything around you will move because of having ground the game until all attack-patterns has been memorized.
And you would likely thus have more trouble with an enemy you haven't ground on, and the only real reason he is not losing is that he at least have a good grasp of his own style, but had it copied any other player he would have lost immediately.