No one ever said such a thing as they were being equals, and we didn't see how it happened or how it went, or how serious it was. WB said there was a duel, based on what he hears, he didn't see it, it's a rumor. Now that you are using rumors to hype mihawk, based on minimum 12 years before when Shanks wasn't even a Yonko, and obviously he got stronger after that, then you are trying to underestimate Kaido's title, by saying it's a rumor. Contradiction here.
What we know;
- mihawk or Shanks wasn't the victorious of their duel
- mihawk got the title without defeating Shanks? If Shanks is only a swordsman, how is this possible?
- Shanks got stronger by being a Yonko years after their duels with mihawk, but mihawk still has the title? Because Shanks isn't just a swordsman.
WB was talking about the ''legends'', the old times what he meant, the duel between mihawk and Shanks was very very old, but he says he still remembers, he also remembers Buggy. Buggy is a garbage, but WB is kind of guy that remembers such a things.
mihawk left marineford because they are not rivals, I just told you, you can't be fooling yourself by thinking that Shanks is a rival to Kaido, but mihawk doesn't want to fight Shanks because he actually thinks Shanks weakened. They didn't fight over +12 years. What he knows that Shanks leveled up by being a Yonko, mihawk never fought Yonko Shanks. Shanks got stronger. You don't become Yonko for no reason.