I’ve had a few bad experiences myself but generally sim checks have been fair. I do remember being jabbed in the back of the neck by one man whenever he wanted to make his point. Another turned up very late, did not brief properly and then went into the sim and pulled breakers and put things out of place. With the increased time pressure caused by his lateness things got missed. Debrief was in the hotel pub and of course, he had no mercy.
However, I have noticed that more often than not the problem is the reverse. Individuals passing through checks, struggling on the same stuff time and time again. Prior to a sim check with X, an examiner told me that X, did not have the faintest idea of how to deal with an engine failure after takeoff during his last check and needed to be taught the whole thing again. Sure, enough, same happens again, X, has no idea and needs to be retrained. Chance of him dealing with that kind of failure on the line are low I would say.
In addition, I would say that blind eye turning is more likely if the subject is a TRE, LTC or manager. As a Captain, I was let off a few times when retraining might have been needed. As for FO’s, they are the most likely to face harsh checking in my opinion.