I believe the DMM 508 2.2.3 is referring to leaving parcels outside but "at box" as was commonly done 30 years ago. To do that now, we must have the form 4232 stating that we can. Without that form parcels must be left "at door", as our scanner gives us that as one of the choices.
True, that nowhere does it say that we MUST drive to that door up to 1/2 of a mile from the route, but that we must deliver. You go ahead and walk it, the rest of us will drive, as the Rrecs time paid to deliver parcels to the door is based on drive time from box to parking place near door to enable dismount and door delivery.
I just imagine what your 2080/2240 time must be if you have a real "Rural" route and walk to all of those doors upto 1/2 mile from their boxes.