Just so we are clear here. The parking brake is the fail over / redundent system to the cars motor / tranny holding your car on a hill. not the other way around.I do for safety, but it is not needed at all. It holds like a champ! I still can't believe it!
Propper way to park on a hill would be turn wheels correct way dependent on how you are parked, shut car off, release clutch in 1st grill. let car settle, then engadge parking brake.
If you engadge the parking brake before you let the clutch out, the motor is not holding anything, and if the parking brake fails, the sudden stress on the gearbox could cause it to fall out of gear and roll away.