Balk-turning the shoulder

[Gre144]

Pitcher is in a half wind up with both hands at his side. He turns his shoulder towards first base. I call a balk.
Was this the right call? The pitcher said that he didn't balk because it is legal to turn the shoulder towards first before the pitcher brings his hands together to come to a set position. I used the explantion that an umpire gave me on this same topic in a previous thread. He said its simple-If the pitcher is bringing his hands together to come set while he turns his shoulders, it would be a legal move. On the other hand, if he is on the mound without any movement and then turns his shoulders he would be balking.(This umpire didn't mention whether having the hands to the side before coming set or having them together after coming set plays a factor in determining if the pitcher balked or not)

Greg