I understand your point.
Since he is closer to the 1 year mark, by the time we communicate and send the green card back to USCIS, he would have passed his 1 year mark. Also it’s USCIS error. They have all his information on when his case was granted, they shouldn’t have approved it in the first place.
Since everyone is trying hard to get a green card well before trump comes to office, it would prove costly to send the green card back. I will update everyone on what is the back date on the card once the physical card arrives.