At this point this debate is redundant.
For the matter, it's factual that a character who fights with a sword can be denied the label of swordsman (King); that a sword that cuts everything may not be considered a real sword and that the strongest swordsman is (at least partially) defined by the extent to which they can choose what to cut instead of their overall strength (Koushiro); and that the concept of swordsmanship has been consistently nuanced throughout the story (Mihawk's skill stressed to be above Shanks's instead of going for his overall strength, Shanks not being addressed as a dai-kengou even though weaker characters like Vista, Ushimaru or current Zoro being so, Law lecturing Tashigi on what makes a swordsman...).
I don't know, for what I care Oda could write a panel on Mihawk being stronger than Shanks in next chapter and I would be fine with it. But it's dishonest that people assume the swordsmanship issue is so simplistic when Oda has made sure to make it the contrary. The fact that Zoro's dream isn't exactly becoming the strongest swordsman but the strongest/greatest/whatever you want to call it dai-kengou is quite telling by itself because, to begin with, dai-kengou doesn't even seem to be a label directly related to strength but something else that allows weaker swordsmen (Vista, Ushimaru) to be considered great swordsmen above stronger sword users (Shanks, Big Mom).
And heck, this is a Japanese story; odds are swordsmanship in this universe is way more complex than just fighting with a sword.