I wonder what kind of actual evidence you have for this. Are you comparing spo dates on the fender tags to the actual VIN decal? If so, there are still way too many variables to get a definite date as to when it was actually finished. If a car was pulled off the line for a scratched molding or to have say the random water leak test done, I'm sure that would have delayed it in getting the final VIN decal slapped onto the car. What about cars that might have been pushed ahead of others for people such as corporate execs who bought a car and didn't want to wait. Again, like I said before, the only way to know exactly what info that is supposed to be on the VIN tag is what was there originally. Once that is gone, and you don't have a pic or other proof, you are only guessing at what "could have been".