again, I'll preface this as my opinion.
Under NFHS rule 6 section 2 article 4 d.
Article 4 If there is a runner or runners, any of the following acts by a pitcher while he is touching the pitchers plate is a balk.
D. Failing to pitch to the batter in a continuous motion immediately after any movement of any part of the body such as he habitually uses in his delivery.
I do not see this motion as continous I see it as 2 separate motions. The hop being a separate part of this delivery. Compared to a conventional delivery it clearly is (to me) not continuous.
That being said..I am for the third time saying that if and when it is sanctioned, I would be more than happy to call it legal. But my thoughts are that if it was legal and provided any real advantage to a pitcher that we would see it widely in the college and pro ranks. I have never seen it done live by anyone. Maybe if I did, I wouldnt see it this way.