The feedback is to make sure the vehicle is immobile before exiting. Take a few seconds to make sure the vehicle is displaying "P" before opening the door. Engage the parking brake on slopes, and let the roll forward/backward until the vehicle is stopped with the parking brake. You should never leave a vehicle until you are absolutely sure that it is able to hold itself on a slope. The original poster never bothered to take this step.As stated above the system is no longer mechanically connected to a lever inside the cabin which provides driver feedback.
After driving manual transmission vehicles for 20+ years, it took one roll away for me to make sure that the vehicle is fully engaged in reverse before exiting. I did this by putting it in reverse, then actually using reverse to move the vehicle slightly if I didn't already back up. This ensured that the gear was fully engaged.