IIRC a team used that Defense against him well before the Bengals did it. There was discussion after one of our losses to KC about why we didn't do it. He struggled against a spy for some reason.
That happened in one of the games last year. Kelce grabbed and fell on our corner and we got flagged. The guy commits penalties on most of his routes. They aren't called and everyone thinks he's the greatest.
If they called a quarter of his push offs he would be a nobody TE. He pushes off almost every route. A lot of the times the play is designed to be thrown right as he pushes off so he's wide open. Refs rarely call it.