I'm not sure I agree with this. IMO trying to get someone to explain the ins and outs of a particular facet of the technology your team works in is less effective than getting a sense of how a candidate architects their code and manages complexity. That type of "art more than a science" craftsmanship is not something you can easily fake in my experience. Maybe I'll be proven wrong. We shall see. So far I've had pretty good luck with the approach and gotten some really great teammates.
It's almost always obvious whether the candidate really knows their stuff. They go into details, when you ask probing questions they don't revert back to generalities or repeat what they already said.
Where this does not work, however, is interviewing junior developers. They don't really know anything at all yet (well, some do, but again, that's almost always quickly obvious), so you're hiring for potential rather than actual skills.