There is information that you don't have. US Soccer produced a video, Managing the Free Kick." I transcribed the relevant parts. Be aware that this, as well as the directive, was published before the spray was approved. IMO, using the spray conveys the same clear message as "wait for the whistle" so there is no need for the "wait" signal if the "I'm marking the distance with foam: message. Note that it is explicitly stated that the ref can make a free kick ceremonial if he thinks he needs to. This bit is part of an example of the ref getting the ten yards: This is what referees at all levels are trained to do. It is also what happened on Saturday.