Tangent question ... as I said above, I know my mechanic is technically incorrect. Can anybody explain to me the benefit of yelling "ILLEGAL!" as the pitcher is pitching? I only see the downside on that.
Since it is a delayed-dead ball, I don't think waiting for a play to complete and then going "Oh btw, there was an illegal pitch' is going to be well received.
I am good with the mechanic saying that I need to let everyone know as it happens than trying to explain it after a play - especially if the play ended up in a strikeout or a line-drive with runners going everywhere. Also, I don't have to run around with my arm extended with people wondering why.
Also since it is an option play, if they know there is an illegal pitch, offensive coaches can coach for it. So the same for an infield fly.
That is my best guess anyway.