RR,
I think the situations that you may be referring to are now UAS folklore from several years ago now. The Bulldog had 2 instances of 'unrecoverable' spins and we lost a JEFTS Firefly circa 1995 in a similar situation. In each case (if my memory serves me right) either:
1. The incorrect spin recovery action was used.
2. The spin was abnormal, ie high-rotational or flat.
Although, I also remember at least one inconclusive report.
As RhoVSquared has said, so long as the AFM recovery is flown accurately, within AFM limits of weight, balance and fuel asymmetry. It is also worth finding out if your ac has a published "delayed spin recovery" in case of the initial actions not working as published.
All told though, spin recovery training is an enjoyable and important addition to any pilot's armoury who intends to practise aerobatics safely - if anyone dares to say you won't ever need it, they really are naive
Enjoy,
Uncle G