I think njarboe feels that it is the human reflex to 'slam the brakes' will fade if the human doesn't use it enough in 'hold' mode, not the mechanism in the car.

Correct. Moving your foot from the accelerator to the brake is a much practiced motion and your body can do it very quickly without much thought. I rarely use cruse control, so when I do and think I might want to brake soon, I get nervous. I don't really know where the brake is. At that point I put my foot back on the accelerator and now my body knows how to hit the brake again.