Alexsemi100 Yes, MARs are contractually obligated to re-image the device and also put the device through the OA3 key injection and activation process ... again. So when the Computer Build Report CBR (which contains both PKID and 4K hash) is generated as part of the OA3 key injection, it is sent to Microsoft where the PKID and 4K hashes are removed from the Autopilot service globally.
Since the MAR OA3 process is tightly controlled (as is the OEM OA3 process) and therefore trusted, MSFT went ahead and implemented this HUGE improvement a few years ago. So any device you buy from a MAR is guaranteed NOT registered in Autopilot.
MARs re-image and re-inject because devices coming back don't necessarily have the license the market needs. Examples: devices returned with Education or Enterprise licenses can't be used by small businesses or home users.
So MARs simply guarantee (!) every device they sell is
1. wiped
2. (freshly) legally licensed according to what it says on their invoice, accredited and backed by Microsoft. No legal hassles here - ever!
3. Activation in Firmware makes ... everything better and easier
4. fully supported by them, fully backed by Microsoft
So your idea to get a refurbished Pro device is great - made perfect if it were from a MAR. They may cost a few bucks more, but IMHO the support (same level as an OEM!), the legal clarity and far less hassle makes it worthwhile.
Ah yes, now I understand why you need physical hardware. 👍