Let it go or balk?

[Matthew F]

Yes, that is covered by another rule and the pitcher is allowed to feint to second base.

So now we have...

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

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 (or feint, since that is allowed by rule) to second base on a pick off play.