I wouldn't call it a balk assuming he's done everything correctly. I would hope that R1 has taken note that the pitcher is now looking dead at him.
However, NAPBL has a paragraph about "ambidextrous pitchers" which could be applied to prevent this sort of shanagan.
6.14 AMBIDEXTROUS PITCHERS
In the rare occasion of an ambidextrous pitcher the pitcher and batter may each change positions one time per at-bat. For example, if the pitcher changes from right-handed to left-handed and the batter then changes batter's boxes, each player must remain that way for the duration of that at bat (unless the offensive team substitutes a pinch hitter, and then each player may again "switch" one time).
So if the pitcher started out as right handed, then switched to a left handed position to try for a pickoff, by the direction given above, he's now stuck as a lefty. Now let's see him pitch to the batter
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Jerry