I've had PPF on the upper portion of the bumper on other cars. Dogs claws will still scratch it.
My solution is to keep a heavy duty moving pad in the trunk at all times (which they enjoy sleeping on!), and drape it over the bumper for entry/exit.
For me, it's the only solution that works. Also comes in handy whenever someone is loading a heavy item and wants to set it down on the opening as they slide it in.