Spencer, please forgive me, I'm going to drift your thread a bit, but we'll still discuss 172's
The 172 is approved to be spun in the utility category, which category has a more restrictive C of G range than normal category. That demonstration of spin recovery (up to six turns) was made with "average pilot skill". In essence, you're not allowed to have people in the back seat for intentional spins, which seems totally reasonable to me. For this configuration, there is a POH spin procedure. There is also the expectation that you could execute a less than perfect recovery, and there is enough "room" that you're not going to exceed a limitation. (The average pilot skill thing).
The 172 (like all "normal category" certified single engine aircraft (+- the Cirrus?)) has also demonstrated compliance with the requirement that it be recoverable from a one turn spin in not more than one more additional turn - at the full C of G range. Indeed, it probably
is the spin recovery characteristics which define the aft C of G limit. However,
that requirement does not require just average pilot skill - it can be demonstrated with some practiced effort. And, the recovery could take the plane alarmingly close to a limitation or two, as long as they are not exceeded.
I can say from first hand experience, that larger Cessnas can approach Vne, and at more than 2 G recovering from the dive resulting from a one turn spin. Not territory to be fooling around in without a G meter!
So, in that way, the 172 has two different limitations, based upon how it is to be flown.
In deference to Spencer's original question, (and respect of thread drift) was you question answered to your satisfaction?