Sure, but a) he didn't know by now much and b) Kizaru, fighting Luffy G4, thought he was strong enough to understand why he had beaten Kaido. Now, trying to say that the Luffy that could be considered as such is the Luffy that defeated Katakuri (a Luffy that is basically G4 Snakman without Ryuo or CoC ) is borderline absurd.
Instead, we saw that even Kaido had a strong reaction when he saw Luffy using AdCoA, so it is logical that Kizaru had a similar one.
More so because there isn't a graphic indicator of the usage of AdvCoA.