CASA inspectors are just that - for the most part, they will not be current on type as in the context of someone who flies the aircraft regularly. Having done this role in a seat behind the crew, it also removes the inspector from the overall situation awareness.
One thing I always used to insist on during the briefing for these scenarios was a discussion on zero thrust, negative torque sensing and VMCA. I had speed and altitude margins that were conveyed to the crew members. Delaying initiation of throttle/thrust lever reduction by a few hundred feet and ensuring a speed margin provided an elevated safety margin (in my view anyway) and the trainee still got the intended training benefit.
As has been mentioned elsewhere, a real NTS event will result in rapid feathering and in many ways is less hazardous than a check pilot heads down at low level trying to set zero thrust.
This is not a criticism of what happened, but a reflection of the reality of checking and training where simulator support is not available.
My condolences to all those affected by this tragic accident.