Where is it stated it wasn't?
Did Katakuri announce BuzzCut Mochi was his strongest move?
Did Doffy do it?
Cracker?
Crocodile?
They never do, do they?
Again you might as well be right but I understood 1037 and 1042 differently, Kaido recognizing Luffy as a strong opponent (just like Big Mom recognized Kidd and Law before going Bigger Mom)
Luffy stating his Haki was getting stronger, Kaido was using a buffer mode to do a even more powerful Ragnaraku. Luffy forcing Kaido to use FS, and Kaido repeating the same move again to finish Luffy (just like Katakuri) suggested to me he was at his max there.
But yeah I could be wrong and Kaido was just taking it easy but it wouldn't sit well it because of how I interpreted these both chapters.