You tell us...you were at the de-brief! Didnt you ask?
Strange.
I always thought when you do a debrief you run through the issues that arose during the flight, why you think they were issues and what you would have done differently. You then ask if the explanations you have given were clear and whether the "candidate" wishes to ask anything.
Then again you could just fail the "candidate" and leave the reasons as a complete mystery - sounds about how things go these days.