You are almost seeing the whole picture then. The ball is placed by the ref. Kelce extends the ball once his hand is on it. This makes it appear the defense is offsides, unless you knew it was the center who extended his arm a foot or two forward. And if you didn’t notcie that the center extended his arm forward, it would look as if somebody on defense is offsides. This is what refs have been looking for this year after being tipped off about it in the offseason.