It's honestly bizarre. They still don't get that nobody is surpassing Kaido, not even by the end of the series.
Oda loves playing power scaling roulette. It spins and spins, and in the end it always lands on Kaido as the strongest of all time. That's how it always goes. Right now it's Gaban, then it'll be Loki, then Shanks, then Luffy. Eventually, it all comes back to Kaido as the strongest of all time because that's the last answer that actually makes sense.