Following up on some references before calling people in for an interview isn't a bad idea.
Man, I have seen some blatantly incompetent ones. You'd give them a white board and ask them to show a linked list with boxes and arrows. They just couldn't do it.
One case I remember couldn't demonstrate pseudo code for a circular buffer operation based on an array with a head and tail index.
Hash tables might be a better filter, because IMHO you're a lot more likely to find those in real use these days than linked lists.
(The job area was embedded development, involving C and C++, so asking for C code related to linked lists would have been fair game!)
And (hopefully) how well they did in the phone screen...?
(These werr people who couldn't program FizzBuzz)
Plus anyone can just make shit up on their resume.