Or it was just allowed to let lie and they said it's an okay thing to do because that's what's in their code?
I think it's a huge mistake to conflate whether someone does know and whether they can know something. Some of the best programmers I've ever seen started off pretty clueless - most of that group learns things absurdly quickly too.
I don't think that exercise gives you good information other than to confirm your expectations. I don't know whether that can tell you if they'll bring value to your organization or not.