Good point about written exams, especially multi-choice. I do find that when it comes to written exams, one thing that is really important is technique and they teach that at secondary school these days. I couldn't tell you a great deal about Shakespeare's plays though I could tell you how to obtain all four marks in a four mark question about them.
The post about HR influence is pretty valid too I think. Where I work, the final interview is done by local management who have direct experience of the role in question. At the end of training it's the same management decision as to whether someone is allowed to become qualified, the decision comes after a four/five day process known as the Initial Competence Assessment.