It comes from the point that the candidate is a lair (when we talk about hiring experienced pros). If someone in your company who is in charge of tech hiring is unable to tell if the candidate is laying about her past experience and projects - you should fire him in the first place (or at least keep him away from the hiring).

So if you want to hire a "guy" to "design your water heater", ask him about the water heater he designed in the previous company, or a water cooler he designed for the neighbor community...