If I were selling a car on ebay and thought I was a pretty knowledgable guy about my Camaros, I would not take the word of a tire kicker sending me an email. Maybe even if someone were to send this gentleman a link to this discussion he may not choose to except the word of all the experts here.
After reserve has been met he can not alter the description. He should cancel the auction, investigate the claim, and at least contact the person he bought the car from if were so recently. JMHO
Maybe he knew about the tag and just dosen't want to lose his shirt?
From Ebay (the within 12 hour rule) If the seller's item has already received a bid/purchase or ends within 12 hours, the seller can only:
Add to the item description, add item pictures, or add a second category. (Exception: If the seller's listing already has a bid/purchase AND ends within 12 hours, the seller can't add to their description, add pictures, or add a second category.)
Cancel is the only option and the right thing to do.(JMHOA)