Do you think it makes Oda less of a writer if ZKK didn't happen after all the presumed evidence, or would it simply be you misunderstanding his message?
I think narratively Luffy will be given that 1v1 victory over Kaidou, just like narratively he had to break Katakuri's myth. It's true Kaidou went through a gauntlet so this is hardly a true 1v1, but Oda always lies in his narratives, he doesn't bother with the details only the end result matters. I think if the end result ends up being Zoro kills a Kaidou that was on his way to recovering even for Oda he couldn't pull off that narrative for Luffy's sake.
There may be room for a compromise here, which is why I asked you what if Kaidou was completely incapacitated unable to move and no signs of recovery. If you watched Naruto this would make it like KKK (Kakashi killing Kakuzu), where Naruto had completely beaten and immobilized Kakuzu, but Kakashi put him out for good after the fact, would this satisfy you personally? How do you envision Zoro killing Kaidou happening?