The idea behind Roger, Rayleigh and Saint Shanks is that they exhibit the idea of classic pirates with cutlasses. However, they are still swordsman. Until Oda specifically differentiates haki as a primary fighting style from swordmanship, they still fall under the category.
Again, the only way WSS logic is broken is if
A) Saint Shanks stops using his sword
Or
B) Somehow hes still stronger than Mihawk even with his title and contrary to every statement made about the duo.
Not expecting it, but the latter I would not even put past Oda considering this very chapter, as Saint Shanks did something Kaido (the WSC) and his contemporary, Big Mom, couldnt even do, and that was reduce Kid's status as if he never beat a Yonko in the first place by literally 1 shotting him. Not even Blackbeard is doing that with Law?
Do i have ulterior motives with Saint Shanks over Mihawk? Sure. Do i think I have any valid arguments other than 199cm vs 198cm, no