Manny, search engine results from another thread
Baseball Discussion Group - 1st - 3rd pickoff Q
Excellent point on breaking contact before throw to 1st that is not required on spin move to 2nd. The following comment supports our viewpoint on the balk, in regards to both distance and direction requirements.
BRD #362. PBUC Staff: During the step to third, the pitcher must leave the pitcher's plate. If he does not, and turns to step towards first, that is a balk.
It's hard to find video of legal 3rd to 1st moves that never work, except for Wakefield's balk video. However, Granderson and Beltran were both caught in legal 3rd to 1st moves while attempting to steal 2nd. Both pitchers clearly leave the pitcher' plate prior to wheeling toward 1st base, feinting there, and throwing to 2nd ahead of the the runner.