Take this with a grain of salt, most humans and animals which humans are a part of learn from their mistakes or should. if you never make mistakes how do you learn or check to see if you are doing something right.
The last thirty or so years I have been involve with aviation I have notice some of the dumbest or worst accidents I have ever seen with the immediate flight crew never having failed a single checkride, oral or written. If you believe that one, then you should look in your backyard for that money tree that is growing.
Wasn't really the learning aspect of it I was interested in, more the 'headline' aspect of how many flight crews put up consistent good performance in the most stressful of situations, FAA check rides that is.
I'm sure that in order to make no mistake during a check ride, many mistakes - enough to cover for the situations encountered during the check ride - have been made and corrected during the training leading up to the perfect rides.