[Tornnight]

This is something I have been practicing forever. I have been a honda owner (Civic then Accord) and they both 'Lock' and thunk if you don't put the parking brake up before putting it in park while on an incline. I always thought that the reason is that all the weight of the car is now on the transmission and it's basically having a hard time disengaging itself with that pressure.

Dunno what your Benzes do differently where this doesn't occur.