You really don't care if someone has a conceptual understanding of UI/UX? I guess that's fine if you're not doing anything unique. But if you are, how is your designer going to be able to think through the unique design problems posed by your product?

I mean - take Mint, which has been widely praised for its design. Would a designer have been able to produce it by cobbling together half-understood components from other sites?

I'd really like to hear more about why you don't think a designer needs to be able to understand what design is. I'm curious about how you think he'd even be able to successfully emulate other sites if he doesn't understand what to emulate and why.