I think it is time to address your assumption of needing to "flush" the motherboards that were being used prior to the ERP. Apple Stores and Apple ASP do not have stocks of spare parts. I was told this by an Apple dealer here in Basel (Ingeno) when I needed to have an Apple LED Cinema Display 24" repaired a few years ago. A part has to be ordered, and Apple expects to have either it or the replaced part returned within a few days of shipping. This is why the dealer refused my proposal to keep the display until the part arrived, at which time he could notify me and I would bring it in. When he had done this in the past many customers just could not bring the device in before he had to send the part back. He was not allowed to use that part to make another repair if it just so happened that, before returning the one he ordered for me, another machine needed the same part.
This means that there are probably only a few distribution centers world wide and they can be tightly controlled. In preparation for the ERP I see no problem with instructing them to send their stock of boards back to, say, a factory on a certain date and sending them the revised boards a few days later, both dates comfortably in advance of the start of the ERP. Yes, in the meantime the distribution centers will have no boards to send to Apple Stores and Apple ASPs who order them, but given careful preparation of the program that delay can be minimized.
We might also have to take leave of the notion that the revised boards need to have markings on them that enable us to identify them as such. In order for their technicians to distinguish them before installation Apple could do something as mundane as package them differently, or paste a sticker on the packaging. Once the repair had been completed and registered in Apple's systems, it would become just another datum in the history of the customer's machine: brought to Apple Store such-and-such on such-and-such a date, diagnosis, proposed solution, customer's consent, what parts were ordered and installed when, results of post repair tests, etc. This information would suffice to determine the origin of the motherboard whenever Apple technicians needed to. I am not saying that this is the way it is. We just do not know.
We just do not know. To my knowledge, neither of us is privy to internal Apple information. We are basing our understanding of what is and is not happening on our experience. My experience is not in consumer electronics, nor in any other kind of electronics, but in the pharmaceuticals industry. People can die if old stock is not "flushed" from the distribution channels expeditiously, and by this I mean not just physical stock, but intellectual as well, as health care professionals may have to be advised on additional precautions to take before prescribing a drug. And yes, in the pharma industry there is an equivalent to "revising" that does not require a drug to be reapproved. In some cultures cosmetic variations in the appearance of a pill (e.g., black specks on a pink pill) suffice for patients to refuse to take them, even though such cosmetic imperfections are meaningless. Companies will go to great lengths to find the cause of such cosmetic imperfections and revise their manufacturing processes accordingly, even if only a small percentage of the yield is affected. Neither doctors nor patients will be able to determine the provenance of a particular sample of the drug thereafter, even though the manufacturer certainly can. In some cases, there may be identifying markings on the packaging, while in others a chemical analysis might be required. In rare cases, tighter quality control is the only answer.
As I have the feeling we (two) are moving the discussion off-topic, I will not be monitoring this thread for a few days.