Because oda must have read hater comments of zoro's title doesn't mean strength or a swordsman with a df it's not a swordsman, so he could beat mihawk etc lol.
The reality is that zoro's dream it's much more than a swordfight and that is proven by zoro's resume.
He has fought against swordsmen but there were other situations that proved that WSS is a title that goes way beyond a swordfight.
King is the best example of what i am talking about, a guy that could fly and use lava like attacks is not your regular swordsman, at least not how the haters were visualising zoro's fights would be.
WSS is a person that is capable of cutting through logia powers, elements, mountains and pretty much everything.
That's one of the most dangerous people in the verse and that is why zoro will fight against any type of situation and rise to the top of the world with his swordmanship.