Regardless you don't have to be the strongest swordsmen if your haki is superior to the WSS. This is the case for Roger vs Mihawk. Shanks haki has Roger's haki potency so even if you want to give Shanks 2nd best, by feats and hype he is being backed/powered by his superior haki.
The reality is y'all need to stop treating titles like they're 1v1 boxing belts, passed down through a committee after 1v1 bouts, if you did that you wouldn't have to do these mental gymnastics of separating haki from the man. I'll bet anything Mihawk is far better at cutting attacks than Shanks is. Shanks' cutting feats will not surpass Mihawk's, that is more than enough a reason for the world to see Mihawk as the WSS.
I genuinely hate shit talking shanks..he's one of my favorite characters but his fans are fucking pea brained retards who zero fucking shame
But obviously though Mihawk at the lowest of lowballs has to be ~ Shanks since being a strong swordsman is all about haki in this verse, and there would be no point to Mihawk being Zoro's goal if he wasn't at the pinnacle as a dfless fighter. I can also understand the other side since Mihawk is the WSS, Shanks has to be below him, but the reality is that doesn't guarantee that either. Roger never held the WSM title, WB did, but through the story we still know they were equals.