Never heard anyone quote that number.
But IMHO if your going to use it to determine a built date by VIN I don't think it will work since we know that on a single day that cars next to each other on the line could be at least 4000 numbers apart and there projected build dates up to three weeks (in either direction) off.
This supports the fact that they did not even consider the cars VIN when they arranged the build order so some cars were built soon after they were assigned a VIN while others waited a while. Longest difference I've seen on 69-70 was a three month wait between when a car was suppose to be finished and when it really was completed