My two cents: Half the electricians don't really, really understand the difference between volts and amps. Half that do, don't really, really understand the difference between AC and DC. Then half of those don't really, really understand power factor. And so on. Somewhere I fall off the edge, too. Yet you don't always need to know how something works, in order to know what to do. And some things an industrial electrician ought to know (like 4-20mA loops) are never required for residential.
There's a popular 2-year trade school nearby. One graduate didn't understand how the seal-in contacts work on a motor starter. Another wondered how a circuit could be both serial and parallel even after wiring four 12v batteries to produce a high amp hour, 24v supply many, many times. Others had been taught to rewire motor starters so the control fuse went to the overload contacts first. They had all passed the trade school tests...
Sooooo... Maybe pay the applicant for a day or two and see what he knows by concepts, or only by facts, out on a job site.