[JRutledge]

It is customary to use the whistle for many substitution situations where I live. It has been encouraged to use the whistle instead of using having the horn blown. For one many tables blow the horn at the improper time. Now it is not encouraged at all times that a whistle is necessary, but to get our partner's attention so they so they do not put the ball in play too soon. It really is not a big deal. I do see why you would want to have the players at the table before the horn is blown. I guess it just comes down to what is taught where you live and is anyone going to make a big deal out of this.

Peace