also zoro kind of predicted what's shusui is capable of when he mentioned that it's far heavier than yubashiri, meaning if he couldn't handle the weight shusui would be useless, so the only advantage shusui provides is it's durability.
even enma that people say it was just free trade solidifies the fact that zoro is special, because zoro's the only one who gets the flaming haki effect when using enma, oden didn't have that.
zoro vs hachi back at arlong park, hachi was bragging that each of his 6 swords weighs 300 kg, then zoro while only using wado and two generic swords of yosaku and johny said that his swords is far heavier destroying hachi's swords afterwards.