Well maybe they were more curious about filesystems and wrote their own? Or they know all about event-based programming but you didn't ask about that because yo

Well maybe they were more curious about filesystems and wrote their own? Or they know all about event-based programming but you didn't ask about that because you don't know anything about it? I think it's wise to avoid "grading" on specific technical questions about things that aren't actually required for the position. That doesn't mean you shouldn't look for bonus knowledge, but I don't think it's good to be too specific about what it is.