then the spin will frequently degenerate into a spiral dive, so this does NOT show the "concept" of the spin (whatever that is?!) and often results in the incorrect recovery being used
Well, yes and no, and no. A properly entered spin in a utility category plane will not become a spiral dive, or that plane would not be certified. Any aircraft for which the spin changes to a spiral dive within one turn of the spin will not be certified without a lot of discussion with the approving authority. This is why the installation of a STOL kit wing cuff on a 150 or 172, will result in a "Spins prohibited" limitation. It simply won't stay in the spin past one turn, as required by the utility design requirements.
So yes, training spin recovery in an aircraft in which the spin changes into a spiral dive by itself is more difficult, though properly briefed, it is a valuable learning opportunity. But, if you're training spins in an aircraft which won't stay in a spin for one turn, something is wrong. Otherwise, if you are following the spin recovery technique specified by the aircraft manufacturer, the correct recovery
is being used. In all cases it's going to include reduce the AoA, and stop the yaw. Minor variations in this may delay recovery, but they will not prevent it. For example, the Caravan POH says to avoid the use of the ailerons, as the up going spoiler linked to the aileron may delay recovery.
As for the Bulldog, I've read about how good they are for spin training, and I'd love to try one - but I'm not aware that there are any in Canada. Everyone who I know who has spun them says they are superior to other training types (in many ways), and how lucky for those who can train in them - but it does not make spin training in other utility types unworthwhile....
A "click" for me is that with proper preparation, I'll one turn spin any certified normal category single engined GA aircraft, for which a spin demonstration is required for certification.