This does make sense honestly.
The scabbards had ryuo that could easily cut through kaido.
Zoro couldn't do this without using enma's power. At least not until he got king of hell.
Does this mean that the scabbards are better swordsmen than dressrosa Zoro? Probably not, given his feats.
However, I don't see how you could use this argument to say Shanks>Mihawk, because Mihawk is only greater in skill. Because as seen with the zoro example, Zoro>Kinemon regardless of Kinemon's better haki. I'm guessing Mihawk and Shanks are the same.