My experience with national rule making (and I've had some in this realm) is that often a "number" in a standard is a conservative "best guess" by the rule makers. In this case, the CAR 3 and FAR 23 spin standard will be based upon what the FAA decided was needed decades back, and that is frequently based upon an awareness of a prior military specification which was suitable.is there a legitimate reason to expect something unusual at 7 or more?
As has been said here, and quoted from a POH, there is no value in continuing a spin much past two turns. I have spun dozens of type of planes over the decades, and I have only once spun (a 150 Aerobat) to six turns - just so I knew what it was like. There is zero value, and a lot of risk meddling around at these corners of the aircraft capability. And, it's just really unkind to engines to drag the plane that high at full power, into cooler air, and close the throttle for a prolonged idle power descent.
The point of spin training is to get in, hold the turn needed to stabilize and recognize, then get out neatly. If you've blundered past three turns doing that, something is wrong.
I have always been amused to read the "limitation" of G forces, when most aircraft have zero means to indicate nor record them!
