The problem is how you understand the titles, why they were given and what was/is their role in the story.
We had Shanks intro already but Shanks hype has been set since the first chapter where he is the MCs goal to surpass by becoming a great pirate and assembling a crew surpassing Shanks.
We get introduced to WSS, this is an absolute title (stated in VC too) because it ties to the deuteragonists dream, it is set to show the absolute strength at that time, the ceiling of individual human power.
Next we get introduced to the WSM, the 2nd Yonko introduction. Here the purpose is to hype the Yonkos, to show how pirates as individuals and organizations are equal to kings/emperors when the Navy has so far been shown as the strongest force. Oda already rectified it by getting the old man to himself accept that he cant be the strongest forever.
Lastly we get introduced to the WSC. People really want to push the Kaido not getting a title box like WB and Mihawk but the point was never about title boxes but why the title was associated with these individuals. Kaido was individually stronger than old WB (we get this from Ace Novel which is canon). The point this time was to hype Luffys opponent and Kaido was said to have got the same effect that Ryuma had in keeping others away from Wano. Additionally only JB could defeat Kaido.
WB already had the fame and WSM (IIRC) while Roger was alive but we know they were equal so you cant be the strongest if someone is your equal. And the main thing is that each of these three WS are of different eras/gens. The gap between Kaido and WB was 15 years, the gap between Kaido and Mihawk is 16 years. So WB was already WSM before Kaido became WSC, yet we know how the Yonko dont go around fighting each other. Kaido gained his own fame and became the WSC. Mihawk came after Kaido and probably never got to Wano due to nature of country and it being guarded by Kaido and BPs. He only got a chance against WB and he lost interest when he saw how weak sickbeard was.
The titles are given by the author to hype the said characters and they are earned when in verse characters witness the feats of those characters. We know WBs hype was because he was the only one who could equal Roger and he had the power to destroy the world. Similarly we got Kaido with the invincibility thing, having an Azure dragon fruit with impenetrable scales, getting only a headache after free falling from 10 km and earning respect everywhere due to his strength since childhood to the point of becoming the embodiment of might. We also get Zoro being mentioned in the WSS debate by in verse characters because of his insane feat in DR and how the witnesses start hyping up the legend.
I have thought a few times of making a compilation of these feats of Zoro and how the legend is being developed by Oda. Just like Ryuma had many legends (one of which was the beheading of the dragon) we will also have a lot of legends of Zoro throughout his journey. You will notice that Oda has specifically given some feats to Zoro that even Luffy sometimes doesnt get in the story, specially when it comes to defeating a lot of members of an enemy. For example, Zoros raid on Arlong Park or the 100 bounty hunters in WP, the magistrate and ninjas in Wano, I am not sure about the 500 gifters in Onigashima though. For some feats Zoro has an audience and for some he doesnt. I think @Fenaker was the only one who would be able to go through the whole story again and conjure up an essay, maybe
@Cinera can,
@nik87 probably wont be doing it. I am just shit at formatting and adding images.