I doubt it, particularly with tail gate supports. But for me it's the stabilizing factor of the weight ahead of the trucks rear axle, and perhaps most importantly, nothing but rubber extends beyond the P5's rear deck, so back in until the tires come to rest against the bed box, no worries, no need to have someone else watch that you're not putting your winch hook through the cabs rear glass, no need for a railroad tie or other at the bottom of the box etc.
A lot of our P5s are different. I have the Honda rear bumper and it sticks out several inches past the rear tires. The rear bumper is high and would hit the truck window if I loaded P5 backwards. On the front, I have a superwinch which protrudes several inches beyond the front tires. The winch is lower and hits the metal of the truck box. Like I said, our P5s are different.
PS: Thank goodness for that Honda rear bumper. I inadvertently backed into the neighbour's car grill the other night. The grill was smashed out but I can't even find a scratch on the paint of my P5 bumper!