Nice catch, but I don't really care. If anything, I like that these small details get tied in and that we might get something about him later on. But it's just trivia.
It's not that bad if you consider that, despite being "the strongest", Kaido was just another obstacle to take down before the final arc. Kaido's role wasn't about what he knew, it was just about him being a powerhungry warlord who took over Wano, and barely at the end he hinted about knowing anything about Joyboy. I never expected anything more from him than what we got, as that was always how he was presented.
The alternative would have been to get the Elbaph arc before Wano, and that would have and it would have been changed the whole plot to a small Zou-like arc with not much relevance outside of cryptic lore.
However, getting the Elbaph arc before Wano would have had the benefit of learning about Nika at least earlier than 5 minutes before Luffy awakened it.