To be fair, the rest of the questions were demonstrably pedantic, and I would completely expect a question like this to be on the bill of fare:

   Q: What does lstat return?
   A: A struct
   >> Wrong, it returns an error code

That type of technical specificity about what well-known functions return is absolutely something I've heard people use as an interview question. Knowing it returns an error code (rather than the value you want) seems like a good indicator of "has actually coded in C" (whereas many other languages return the value you want and raise an exception if it had an error).