I know this, because I used to look at resumes and have long conversations before I ran my pairing interview. And I found the results almost uncorrelated. Now I save the fun conversations for people who make it through the screening. But by then I already know if I want to hire them.
My pairing interview (it's a pairing session, not a code challenge) covers aspects of engineering that I specifically care about. It's not terribly hard. But at the end I'll have a pretty good idea if I want to turn this person loose in my codebase.