Not true, Steve. In FED, going to the mouth while on the rubber is "a motion associated with the pitch" and is a balk. While 6.2.1A and 6.1.2D only hint at this ruling, I seem to recall an interp that deals with it directly.

Here might be that interp:

From the BRD #363

"If F1 goes to his mouth while deliberately in contact with the pitcher's plate, he has interrupted his pitching motion." 6-1-2. PENALTY: Ball/Balk (6-1-2 Pen)