[TeMPOraL]

It doesn't if the examiner understands the material. You can't bullshit someone who knows much more about a topic than you do - bullshitting with confidence will only make you sound like a fool.

If the examiner isn't much more knowledgeable about a topic than their students, then something else has gone wrong.

[jrumbut]

But you can appear to know less than you actually do through a lack of confidence.

[ska]

Right, but that's why it takes a bit skill on the part of the examiner - you need to be able to support people through their nerves and lack of confidence.