Let it go or balk?

[Matthew F]

How does 8.05(a) pertain (if it does)?

8.05 If there is a runner, or runners, it is a balk when-

(a) The pitcher, while touching his plate, makes any motion naturally associated with his pitch and fails to make such delivery; If a lefthanded or righthanded pitcher swings his free foot past the back edge of the pitcher's rubber, he is required to pitch to the batter except to throw to second base on a pick off play.