ASA SP Mechanic

[NCASAUmp]

Someone brought this question up, and I'm not quite convinced of the answer that I got. Thus, I throw the question out to you...

ASA 6-1-E: The pitcher must not simulate a legal pitch while not in contact with the pitchers plate.
EFFECT: A dead ball should be called, an illegal pitch ruled, a warning is issued, and repeated action would result in the pitcher ruled illegal, and removed from the pitching position.

I was told the proper mechanic for the PU would be to signal DDB and call "Illegal." Then, kill the play with a "dead ball" signal (verbal and visual). Then, step out and warn the pitcher.

Why bother with the DDB signal? If the effect is a dead ball, why not skip the DDB signal and go straight to "Dead ball!" instead?