To randomly pick on something during a training flight with a pilot you're not familiar with, and then when you find the pilot can't cope, to attempt to rebrief in flight, is a really bad way to instruct.
No it's not - he gave the student a simulated emergency to see what he would do - the fact the student didn't have a clue was unfortunate but he might have been the same with any 'unbriefed emergency'. If you feel you can only initiate pre-briefed emergencies with a student, whether you know him or not, then you should look at your own instructional competence.
It may be the way it is done for OPC/LPC in the N Sea to tick boxes but for the real world where emergencies and problems don't come ready briefed it is a pretty poor show.
And I am arguing with you because you had the gall to pounce on Hughes500 and criticise his professional competence without knowing the context or any real details of the sortie. And I get criticised for being arrogant................