Are you saying that the hardest rudder pedal does not indicate the yaw direction in spins?
It does in 1 type I fly... as the "backstop recovery" (POH) if you are unsure what is happening. It is
not the Spin Recovery Drill.
I have never heard it
taught on any type I have flown. I have never taught it. I would never teach it except where specifically recommended. I cannot see how it would work with power / non-reversible controls. It certainly will not result in the optimum recovery.
the accident brief you cite sheds no light on what actually went wrong
It sheds a lot of light, IMHO, about taking spin recoveries seriously, type specifically, and does not mention pPrune as an "authoritative reference"
The OP is starting out spinning, and asked some rather generic questions. I believe it worthwhile deflecting him from the advice above, and pointing out that it is a subject that can, and does kill, if not approached correctly.
Just my opinion
NoD