If you shoot a 50 grain load your bullet will rotate within the barrel a given number of times. Does that change with a 100 grain load? No, the only thing that changed is the time it took to travel the length of the barrel. The flight time to the target will also be reduced (though a very small amount within the range of hunting loads), so the bullet will make the same number of rotations in minimally less time. If you want to look at that as more RPM, ok, but it is not more rotations between the muzzle and the target.
I disagree because I believe that the RPM's are increased after the bullet exits the barrel when loading with more powder and velocity instead of less.
That's because the bullet will spin faster due to the increase of inertia/momentum from being launched through the barrel at a higher rate of speed.
IMO the bore acts like a centrifuge on the bullet rotation. When the bullet zips through the barrel faster, it will rotate faster after it leaves than if it was propelled slower and by less powder.
The bullet is no longer constrained by the original twist rate inside of the barrel but is free to rotate faster as dictated by the effect of the increased momentum and velocity.
I believe that's the reason why some some powder loads and velocities will stabilize a bullet while other loads won't. Everything is basically the same except the amount of spin imparted to the projectile which affects bullet stability.
It's mostly based on the velocity and related RPM's needed to stabilize a specific bullet profile exiting a barrel having a specific twist rate. Different twist rates besides the optimum can often work if the powder charge and velocity is adjusted.