Everyone who is competent with a sword and uses it in battle, is a swordsman. However it is questionable whether each and every swordsman falls under the WSS title or only those whose strongest asset is swordsmanship. Law is a swordsman, but his power almost solely derives from his devil fruit; his abilities are not based on swordsmanship or the sword at all. While without his DF, Law was stalled by Doffy's clone. So it would be odd to strip Zoro from the WSS title because he cannot beat Law's DF, when Law's actual swordsmanship is trash compared to Zoro's.
It's another matter if the swordsman has a DF but that DF is a weaker power than his swordsmanship. King is still a contender for the WSS title, because his Zoan merely enhances his physicals (and thus his swordsmanship) and King's fire is probably not nearly as effective as his swordsmanship.
It makes sense to me because otherwise, the WSS dream would encompass too many important characters, since 99% of the relevant characters are using swords. Mihawk, Shanks, Big Mom, Roger, Xebec, Shiki. And story wise, the WSS is portrayed as a PK's right hand man material. So it would be Odd if Zoro was the one to surpass all these characters.
Another question that might arise is, why didn't Mihawk challenge Big Mom? It was said that Mihawk, after Shanks lost his arm, continued searching for and fighting strong swordsmen until there was no one left. But somehow he never crossed blades with Big Mom, who 12 years ago, was surely stronger than Shanks, since Shanks was young while Big Mom was pretty much at her prime. Nor does Mihawk challenge Big Mom now. I mean you can argue between who is stronger between Shanks and Big Mom, but still, why would Mihawk not challenge a Yonko level swordsman while fighting other swordsmen until there was "no one left".
Thus I believe that people like Big Mom and Shiki too wouldn't fall under the WSS title. Roger? Theoretically, but we have yet to know his full power, the one that allowed him to match the Gura Gura no Mi. I believe it might be a very advanced form of CoC. Since in terms of swordsmanship, he doesn't seem to be on Mihawk's level (not even having a black blade) but yet being obviously stronger.
It's another matter if the swordsman has a DF but that DF is a weaker power than his swordsmanship. King is still a contender for the WSS title, because his Zoan merely enhances his physicals (and thus his swordsmanship) and King's fire is probably not nearly as effective as his swordsmanship.
It makes sense to me because otherwise, the WSS dream would encompass too many important characters, since 99% of the relevant characters are using swords. Mihawk, Shanks, Big Mom, Roger, Xebec, Shiki. And story wise, the WSS is portrayed as a PK's right hand man material. So it would be Odd if Zoro was the one to surpass all these characters.
Another question that might arise is, why didn't Mihawk challenge Big Mom? It was said that Mihawk, after Shanks lost his arm, continued searching for and fighting strong swordsmen until there was no one left. But somehow he never crossed blades with Big Mom, who 12 years ago, was surely stronger than Shanks, since Shanks was young while Big Mom was pretty much at her prime. Nor does Mihawk challenge Big Mom now. I mean you can argue between who is stronger between Shanks and Big Mom, but still, why would Mihawk not challenge a Yonko level swordsman while fighting other swordsmen until there was "no one left".
Thus I believe that people like Big Mom and Shiki too wouldn't fall under the WSS title. Roger? Theoretically, but we have yet to know his full power, the one that allowed him to match the Gura Gura no Mi. I believe it might be a very advanced form of CoC. Since in terms of swordsmanship, he doesn't seem to be on Mihawk's level (not even having a black blade) but yet being obviously stronger.