Punk Rotten's AP is comparable to G4, not G3.
G3 didn't make Kaido feel any pain whatsoever
Punk rotten was confirmed to have bypassed Kaido's durability and made him feel at least some pain(as evident by his scream and his own admission), even if the move didn't draw blood.
Given how bad act 1 Luffy's portrayal was, you could even argue that Punk rotten was above G4.