That's interesting and if we look at his hype with a little bit of Nuance, it would make sense.
I think its a case of perception vs reality, when perception to the world is that Kaido has won his battle with Oden, reality is that he won due to taking unfair advantage. Perhaps it could be that Kaido has won majority of his fights through cheating, dirty tactics, hostages etc but world just looked at his victory record and ran with the idea that Kaido is invincible in 1v1 battle. I think Oda did that on purpose because he doesn't want the man who represents peak of One Piece power scaling to go down in the middle of the story.
Perception vs Reality was very much evident in whole cake Island with Katakuri's siblings buying the false perception that Katakuri has created with his made up perfectionism and a victory record that is supposed to be legendary rest of the world doesn't care about. A record so irrelevant to the unbiased people of the world that they don't recognize him as king of 1v1 fights, instead they recognize Kaido as one. So much so that Big News Morgan didn't even mention Katakuri's undefeated record while giving Luffy his 1.5 Billion belly bounty, I mean he didn't even specifically name drop Katakuri, instead he was just one of the two sweet commanders that Luffy defeated. Obviously if Big News Morgans bought false perception of Katakuri that his siblings did, his defeat would be one of the main focuses of his new article. There are many more examples but I feel like it deserves a thread of its own.
Anyways point is, it is very possible Kaido's reputation is simply a result of false perception the world has regarding him and not that he is actually all that.