"Im guessing there was no distinction made and the buyers didnt even know." with this you mean the buyers weren't aware that the car they were getting was used for testing earlier?
in the case of the GTR I was talking about absolutely yes. there was a white NISMO GTR that a guy on GTRLIFE was interested in at a FL dealership. he simply asked if anyone knew about the car. I went and did some research for him and ended up matching the VIN # to the exact car that motor trend did a review of and was used for the laguna seca lap. so this car probably spent most of its life on tracks or beaten. the member of my site didnt end up buying the car and im not sure what happened to it. If he wouldnt have posted on the site and I didnt happen to find a pic of the door panel on motor trends website where I zoomed in and matched the VIN he would have never known
there was a less drastic example of this where a guy on GTRLIFE was asking about a matte gray NISMO. that color was really rare and eventually discontinued but we were able to use a GTR registry online and track that VIN back to a car that nissan used at various autoshows months before the car was available for sale. it eventually ended up at auction then resold.
so there are a few cases I know that this happened with that particular model GTR. the autoshow car isnt a big deal but the one that had been used for all the car magazine reviews I would have been mad if I paid $150K+ and didnt know.