So you do acknowledge that Rocks roger> kaido?
So that's clear portrayal for shanks.
Second. Kaido isn't infallible. He's not 100% reliable like the narrator is. He's just another character. And kaido is a very prideful character who prides himself in his strength.
Him saying only joyboy can beat him is just him believing his own hype lol.
Kaido said that no one can beat him while getting his ass kicked around by Nika goofy. And said that luffy can't beat him. Then proceeded to do just that lol.
So is kaido a liar? Or is it just him just hyping himself up?
Kaido is monologuing luffys Nika power awesomeness while saying no one can best him lmao. That's how you know that even kaido doesn't believe what he says.