Let me hypothesize: If this attack from Luffy actually knocked out Kaido, what will happen? I can pretty much guarantee you that Luffy will not finish him off. There are no marines to capture him, and even if there were, then what was the point of Kaido's entire introduction? We were told that capturing him made no real difference. In Kaido's intro, the narrator literally says "I
repeat" when talking about the inability to restrain Kaido for good.
So what will happen then? Luffy and co will go celebrate their victory over Kaido and the party begins and all that shii. But because of Kaido's nature, and the fact that there is no one to actually take him away, he will inevitably...wake up. And being the arrogant fucker that he is, he will try to cheapshot Luffy and the Flower Capital after his defeat. Why? Kaido's philosophy in a nutshell:
And in dramatic fashion, in order to save his captain, in order to save the people of Wano, and become the new generation's legendary samurai figure, Zoro will slay Kaido.
Would that take away from Luffy's victory? No. He defeated Kaido, the same way he defeated every other villain he's fought. The literal only difference between this time and the other times would be that there was no one to conveniently take Kaido away on a stretcher. And even if there were, it shouldn't matter...because it's Kaido.