I would expect another interview purely to gauge likeability/communication/basic hygiene; this is a good approach just to gauge raw programming skills. It's no use getting to know someone just to find out they can't code at all.

That being said, the benefits of being able to discuss the requirements/expectations of the test would probably outweigh possible negative biases. Even if the candidate doesn't know what refactoring is, a discussion about it may give them insight on what they should research to increase their employability.