Thats what people don't understand about NOS stuff. ALL of it came from the Service department. When a completely new car came into production part of the servie organization at GM had to go thru each and every peice that they needed to have on hand, and decide if an existing part was Functionally equivalent to a part on the new car. If so they stocked the funtionally equivalent part. If there was nothing out there that could be used, they stocked that part or parts. Over time as other lines changed, were added or deleted the definition of functionally equivalent got looser and looser. Most servie parts are not the same peice that came on the car originally, and the further away from the year the car was made makes it even less likely the part was actually even used on the car originally. Look at NOS trim rings as an example. Production cars had either the 4 clip retainer or the dragons teeth retainers design up to at least late in the 69 model year, some had D shaped valve stem holes, some had holes open to the inner edge, some are oval some are round yet every NOS trim ring has the multi finger retainers and oval valve stem holes that came out late in 69.
Service parts are not production parts. If people want to pay stupid money for incorrect parts have at it.
The term used widely now is 'form and function'.