Yes, as Mihawk is a pure swordsman, and the best opponent he's ever faced was Shanks when he had both hands, he really expects someone to defeat Shanks in fencing, even with one arm apparently Shanks is second on Verse in fencing. But if by chance Blackbeard beat Shanks, Mihawk will run to face him since he beat him, right? This quote from Mihawk only sums up sword skill, not full strength. Blackbeard defeats Shanks...
And Blackbeard is not a swordsman... LOL. This statement is abstract and limiting, it only involves the skill level between swords, shanks can be bested by someone in a sword duel, but they may have to use "other" means, eg haki he has specialized in over the years. years when he lost his arm, to beat his opponent, in general and in short, shanks is inferior to his opponent in swordplay, but not in full strength. Another example:
Kaido is a pure swordsman expects someone to beat BIG MOM his rival in swordsmanship... Big Mom can lose in fencing to X, but can beat X using his DF or something next, but in fencing X he beat Big Mom, that means X is the person Kaido was waiting for, even if he's weaker that BIG MOM in general power.