It's hard to tell what Oda intends to say here. Swordskill = power. Evident by Zoro amping his skill with CoC. And now Xebec's swordsmanship is brought up. Now how does Shanks fight? He doesn't have a fruit, he only uses his sword and Haki, so same thing Zoro does. Cutting or not. He had Kamusari when he fought Mihawk, so shockwaves are in the equation.
But then again, as
@ZenZu pointed out, why not just saying "with a power surpassing emperor Shanks".
You could argue, Oda does it on purpose. He wants the ambiguity.