I'm no examiner but i talk when i'm with someone else.
i reckon if you are telling them whats going on it lets them know you have a bit of a clue whats going on.
Its also handy to vocally readout checks you are performing so he may be able to guide you in the right direction should you have missed anything. I know i would prefer to pop on a fuel pump or carb heat should it have been inadvertantly forgotten (as we all have before)
Good luck with the test. You can get on with having fun soon
F.