In reality, that 10% failure rate is true for most all NOS BBDs, we are just trying to be honest about it.
That said, the whole "NOS" thing is, IMHO, a bit of nonsense. Here is an un-official take: Panasonic/Matsushita stopped making BBDs like 15+ years ago. It seems improbable that there were such huge stocks in storage that 15 years later they can still be bought by the thousands. It is more likely that somewhere in China is a fab that is cranking out MNxxxx chips from the original masks, stamping them with the old "M" logo, and selling them as "new old stock" - which gives them a pass for poor or inconsistent quality. We list them as "NOS" because that is how they are represented and we have no information otherwise.
Stuff like this is why we built our business on (only) new current production parts purchased direct from the manufacturer. But the chip shortage/pandemic are putting builders out of business, so we do what we can to keep the parts flowing. No matter all the NOS nonsense, by and large they do work and in the end that is all that matters.