I mean, if I was Zoro, I wouldn't expect some random Mink to start using Rokushiki.
It's less that Rokushiki would surprise him, and more there's no reason for him to think Minks know those abilities, when, as far as he knows, they're limited to the WG.
Edit: I wish I was clapping Wanda, still. I've come to really like the doctor Squirrel Mink too (Tristan).