It's also why slamming on the rear brake can be so dangerous, locking up the rear wheel is much more likely to send you into a highside.
It's "released" in the sense that once the tire regains traction, it throws you over the bike into a highside. What usually starts that is locking up the rear wheel under braking. It's why I do 70-80% of my braking with the front wheel. It's where your braking power is (I ride a Ninja 1000, other bikes can be different somewhat in weight distribution.)I thought releasing the skidding rear wheel is what causes high sides.....?