He's probably also disciplined enough not to sound off on topics that he doesn't know anything about.

I was consulting (software) at a client site and one of the employees at the client remarked that I seemed to know everything about everything. I just replied that it was a trick - I only talk about the things I'm informed on, and when a question came up on a topic I didn't know anything about, I just redirected the conversation back to my expertise. I had a hammer and worked hard to make everything a nail. :)

So... when you're not a consultant with a need to impress people, you instead redirect the conversation to subjects other people know, which interests you? :-)