Just because Kid used Punk Rotten alongside Luffy doesn’t make it his ultimate form or technique. I mean in that same image Law isn’t using gamma knife, are laws rocks gear 4 or even punk rotten level? .... Punk Rotten doesn’t even have any drawbacks like Gear 4 does, nor does it drain stamina like Laws DF, it can take hits, get sliced and still reform, it has enough physical strength to pick up Kaido in Dragon form and it’s size is greater than G4. Doesn’t mean it’s his comparative form just because he decided to use it then. It’s not like everyone who’s not Luffy has forms like gear 2, 3, 4 anyway lol