When doing IT people often say "Well, I don't know anything about computers", which I generally found pointless, as with about 30 seconds of talking I can tell if you know anything or not. Your story passes my smell test, as getting someone talking is 90% of telling what they know.
People with broad and deep understanding of technology can typically gauge if someone knows there stuff or not with 30 minutes of them describing a system to you and answering questions about it.
