Using this same principle though we can argue that someone who knows nothing about brain surgery, such as myself, is qualified to hire brain surgeons based on whether they can explain how to do it in a way that I personally think makes sense to me. I might like to commend myself for being able to hire brain surgeons by virtue of my own ignorance, but it seems to me that the flaw here is I don't really know whether what he explained is true, or if it just sounds good.
You can't make too big a gap--I certainly wouldn't recommend non-technical people trying to hire engineers this or any other way--but maybe it's still possible for a reasonably smart engineer to identify an even smarter engineer.
That's how you know they actually know what they're talking about - the ability to explain it to their grandmother.