Is this a Balk
 

13U modified OBR, R1. RHP engages rubber, hands apart, as he would in the set position except with free foot pointed to the the 45 as he is watching the R1. After a second or two he moves the free foot to point to home, still engaged and hands still at his side. He then proceeds to stretch, set and deliver normally.

Edited after mbyron's post below: He is moving his entire leg 45 degree, not just where he is pointing his foot

I am wondering if that movement of the free foot from the 45 toward the plate is a balk. The OBR states, "...he shall go to his set position as defined in rule 8.01(b) without interruption and in one continuous motion" But does this foot movement constitute the start of the preliminary motion?

At that level, I'd say no. If he does it routinely, I might speak to the coach about it, as I might get that in a varsity game. But even there it's a pretty small violation: he can't be set with his hands still at his sides.

Technically, it's a balk for starting and stopping: whether or not it's part of a "preliminary motion," he's coming set in 2 distinct motions, which violates the "one continuous motion" requirement.

rec league - I'm saying something to the kid and the coach

13U USSSA/travel ball - I'm calling that all day everyday.

13U, I let it go.

14U, it's a balk.

Wait, maybe this us the one I let go at 12U, and call at 13U.

Or, maybe it depends on whether the pitcher shaves.

Or, the majority of the team shaves.

Nope, repositioning the free foot (other than as part of the initial
getting comfortable on the rubber), is a balk from me.

The kid is just screwing up the timing of something he's seen:

Perfectly legal and common: RHP engages rubber in set position with free foot/leg open towards first while taking signs. When he comes set he brings his foot in to a more natural position at the same time his hands come together. No problem.

Balk. Many of the umpires I have trained offer classes that teach the proper and improper procedures around and on the mound preseason especially if they are not OBR rulesets.