The bass, the finish, the woods used, none of it is "Old Stock". Maybe if they were using a pot of finish/paint from the 60s, or woods from the 60s. Or something that qualifies the word "Old" being used. Before reading this thread, had I saw a Fender Custom shop bass be described as being NOS, I would have assumed this was a body and/or neck stored in the factory for 50 years, which would be pretty cool and well worth the ££££ to some I'm sure.
Again, I'm not trying to be argumentative, I just still haven't heard a reason why they are using this phrase to describe a finish. But i realise a byproduct of being unsatisfied with justifications posted is indeed turning out to be argumentative, so I'll stop 😅