Checking 1B prior to set, heel comes up

[umpjim]

This looked weird to me in a PONY (OBR) game with pitchers and coaches still a little weak on balks. The pitcher prior to coming set checks 1B with a shoulder turn. This pitcher while turning to look at 1B lifts his pivot foot heel about 3 or 4 inches when he does this. I told pitcher and coach don't do this or I will balk for a feint. He managed to turn without lifting after that. Am I offbase?