When I used to conduct engine offs on a GFT it was very much a solo effort on the part of the examinee - but the air of nonchalance was entirely contrived and I was ready to take control in the final stages if need be! Naturally if that happened I'd congratulate the student on a good attempt and ask him to show me another one just like it, only better. This used to relax them as they felt I had confidence in their abilities. I don't remember anyone that I flew with failing a PPL test for failing to complete a satisfactory engine off. I wasn't looking for anything like perfection - just the ability of the candidate (and any passengers with him) to survive if it should ever happen.
try pulling the mixture to lean/Cutoff at 2000 ft, then switches off, fuel off......and your on your way.......the total effect is far different to just closing a throttle.........the silence is deafening to start with, the required NR control is far more sensitive with no residual engine power........until you practice that, you can't claim you practice Engine Off to the ground.
Can't say I've noticed any difference at all in Nr control, though the noise is marginally less. In 1990 Eurocopter had a problem with a faulty batch of freewheels on the AS350B and it was not permitted to reduce power below a certain level without shutting down the engine - naturally that required the engine to be shut down for all autos and EOLs. The requirement was only in force for a fairly short period of time but it certainly helped to concentrate the mind when conducting training or tests!
