More that he should have a very reasonable expectation that the candidate already has the requisite knowledge.
I have an
expectation that every candidate that comes to me for a skills test is ready to demonstrate that they can control an aircraft - but I guess my idea of preparing a student for test is different to others. I've had some appalling candidates in front of me both in terms of theory and practical.
At the end of the day it is my responsibility to assess that candidate is safe and I take that to mean I can check if they can explain separation in class D airspace, can tell me where they can find more information about the DOC of the ADN VOR, can describe the braking system of the aircraft they're flying.