enemyMiG, in addition to what Plaz has said, there are only a couple of reasons he would have been in the sim during the final stages of his training.
There was a major aspect of what constitutes normal ops that wasn't seen during OJT - luck of the draw or some external factor such as long term closure of military airspace during the training & the instructor wanted to ensure he'd seen how to handle it.
Or, given the fact he was terminated, there was a major deficiency in his controlling & he'd made the same mistake repeatedly. In such circumstances the sim is used to specifically test that deficiency by demonstrating you can correctly handle it (or not). You aren't expected to be perfect but must be handling the basics competently & the odder stuff at least safely.