Just because a part passes memtest86 and a couple of hours of Prime95 does not mean that that part is interchangeable with the genuine article, especially as fa

Just because a part passes memtest86 and a couple of hours of Prime95 does not mean that that part is interchangeable with the genuine article, especially as far as an OEM who is trying to meet requirements is concerned. With a counterfeit, you have no idea what the MBTF is, no idea what the specific electrical properties are, no idea what the errata are, etc. etc. Even moving from an obsolete/last-time-buy part to the manufacturer recommended replacement might not go entirely smooth.