Evan, seems you said it all, as always. BUT, I have to connect this practical knowledge to the "theory". Advice given by others is great as well to help me understand.

Two main factors defined in the NASA report, calculated for my favorites:
No surprise: That means our models are well below the density range of full-size airplanes. (The report starts with values of 6 and 10.) Still it's true that more density needs more rudder for spin recovery, or maybe low density needs even no rudder.

Well a surprise (for me) is the clearly negative inertia parameter of our models. (The "neutral" range is defined as -0.005 to +0.005.) That means the masses are distributed more along the fuselage and not the wing and in that case the primary control for spin recovery is aileron, according to the report. (For wing-heavy airplanes it would be elevator and for "neutral" ones rudder.) My (electric) glider has +0.012 (really measured) so the aerobatic models have a way too heavy tail (to be "neutral" ). A caveat is that the moments-of-inertia are (educated) guesses, but we're in the ballpark and clear is that a heavy engine up front and servos in the tail make things worse.

The third most significant factor for spin behavior is tail configuration, but the parameter is hard to calculate (means I'm too lazy). As to the significance of these factors for models: Same air, same rules!

The report not only states that for fuse-heavy planes the aileron is the primary recovery control, but also that it should be deflected with the spin! Evan, that confirms my suspicion that the spins (and snaps) done the usual modern way might be not developed spins but maneuvers looking alike but smoother and better controlled. And that seems to be the point, a true autorotation with much elevator doesn't look as good as a similar rotation driven and controlled by the ailerons and not really stalled. For me, that's the main conundrum.