Hey guys,
I figured out why the memory issues exist when not using the data bus to operate the head unit, and, the simple answer is that when on a class 2 data bus, the head unit essentially never really shuts off completely. Instead, the head unit goes into a "sleep mode" type of function so that it may remain powered on for such things as chimes and OnStar. This continous hidden power on mode is what also keeps the unit for loosing it's memory.
The head units also used to act as a communication bridge middle man for OnStar and needed to be "awakened" at any given time for this system to work. By the time the GMLAN head units were released, due to queues from Panasonic, both GM and Delphi figured out a way to connect Onstar directly to the BCM, but, also have the head unit power completely down, yet still able to power on at a moments notice.
I haven't figured out yet how to re-enable this "sleep mode" in the units at this time.