I think I can comment, having not only been taught by a reputable shool (my groundschool instructor for my FI(R) had been an instructor for 50 years) but also having taught Principles of Flight at ATPL. DFC is entirely correct. The 1g stall speed of a conventional, certified aircraft will always be higher power-on than power-off. The aircraft could not be stalled if the nose dropped above stall speed, and this would suggest to me that the aircraft is way outside the C of G limits.
Assuming that he has correctly reported the briefing, this FIC instructor was talking garbage. That is worrying. I think someone should be told, starting with the student. However one would hope that, having passed at the very least an approved CPL groundschool course and have a couple of hundred hours or a CPL the student should have an idea him or herself. Perhaps just talk about it, to see if that is the case, confirm that the student is right in any doubts, and encourage a complaint. The paying customer complaining can sometimes get things corrected most quickly.
As Mach1.1 hints, we hear about many badly-taught FI(R) courses. help the students who suffer them do something about it.