That would also be the case in the "wrong tee/ball" play. The offense tricks the defense into thinking the ball is dead...and that play isn't legal. What is the difference in this play that would make it legal?
Not at all saying this should be legal, but the difference you ask about is the "prop" being used in the "wrong tee" play, and the communication with the sideline in the "wrong ball" play. A somewhat blurry distinction, yes. But, I have experience with a team attempting a play in which the QB, in a shotgun formation, calling signals, suddenly raised up, turned and started walking briskly toward his team's sideline, shouting and gesturing with his arms. It wasn't the "wrong ball" conversation, but something having to do with confusion about the play to being run (i.e., "Coach what's the play?"). As I watched this unfold, I recalled a similar thing happening to PAC 10 R Land Clark (now in the NFL) the previous year, and he flagged it for UNS, and was judged by Redding to be correct. So, I flagged it, as well, and also got a correct call judgment (by my coordinator and Redding). (FYI, they did snap the ball and run a play in both instances, for a live-ball foul.) However, Redding pointed out that what made this UNS was the gesturing. Had he only turned and moved (walked, trotted, or run) toward his sideline, without any sort of hand gestures, it would have been legal.
The "deke and run" play would seem to be like the scenario in which the QB turns and moves toward his sideline without making any gestures, with regard to legality. They both fit in the same suit with regard to sportsmanship - questionable, but, technically, legal, since they don't use props or communication with the sideline. Perhaps that is the logic used by Redding and Shaw for this current ruling. I can't say.
But, the biggest difference is how each play relates to player safety. The "wrong tee" or "wrong ball" don't affect player safety anywhere nearly the way the "deke and run" does. Now that we've all been told this action by the receiver is legal, kicking teams will err on THEIR side - not the side of safety - and will clobber the receiver, if they have any doubt about the possibility of the receiver attempting to advance after the catch. They'll take 15 yards, if it prevents a TD. And I guarantee you, their special teams' coaches will tell them to make it worth the 15 yards (and even a possible DQ), so they'll think twice about doing again.
And that is going to get somebody hurt.
I hope the committee hears these concerns, and takes action on this for 2019, if not sooner. But, I fear someone will get badly hurt before they take any action.
Robert