NFLs statement on this...
I did not know this. Learn something new all the time. Also, I did not see an illegal shift. I did see a receiver was still getting to his initial spot to set and wasnt set in time. I guess that is what they are calling the illegal shift. Not entirely sure how that rule plays out to be honest.
Also IIRC you cant really overrule a whistle that blows a play dead and the whistle blew before the ball was recovered. How is that fair if they blow a play dead to give the ball to the other team.