In theory this statement makes sense, but several factors must be considered.

1. If the system evacuation is done CORRECTLY, several ounces of oil will be removed along with the refrigerant. (With the vehicle at operating temperature and the A/C on, the evacuation should begin immediately after the engine is switched off)

2. Has the system had any leaks repaired in the past? MB work instructions recommend a certain amount of oil be added depending on what part was replaced, but if the system has lost ALL refrigerant it most certainly has lost some additional oil as well. In fact, the oil is what makes it possible to visually diagnose A/C leaks in the first place.

3. I'm glad you mentioned the GM R4 compressor. This unit was not exactly known for it's durability. My 91' Buick has one. After fifteen years it's still using R-12 and it's as quiet and efficient as when it was new. If it weren't for periodic TLC it wouldn't have lasted this long.

Your instructions on how to properly FLUSH an A/C system are right on the money, but from a maintenance standpoint I think it's overkill. A total system flush should only be necessary if there's been a catastrophic compressor failure. On the other hand, if a DIY'er has access to the proper equipment and doesn't mind spending the time, why not? I certainly wouldn't recommend paying to have this done as a preventive measure though.