But you could tell something was fishy by listening to him. You said you got the impression he taught the whole story rather than lived it. That's exactly what you are looking for; that's why it's so valuable. A real developer can tell when someone is bullshitting him in about 3 sentences.
Having said that, let me be clear. This isn't a good tool if all you have to do interviews is a manager. They probably won't be able to tell the difference, especially if they are just generic managers with little to no technical experience. They aren't the type you want giving technical interviews.
I have not interviewed many people yet, but already during one lunch (!) interview (where I don't ask any questions), a guy was so proudly talking about his achievements at his previous job in quite generic terms, that I've got an impression he was teached the whole story, rather than actually lived it.
Later he was not hired. According to (trusted) others in the interview loop he did not know how to do any basic shit.