I did not hear back, so I decided to call. Spoke to Patrick, he said "Oh we get these calls often, and your the 3rd person that has called on this car, saying the tag is fake". I asked "does that give you pause then?"
Oh no, we have a guy thats been doing this for 18 years (Paul) and he checks them all out. Patrick says he thought he overheard Paul telling a customer on the phone that he has special GM Docs that show they used X codes early on. So Patrick is going to have Paul get me that doc, or contact me and let me know why this car is real.