This would be a very unusual pick off move since most pitchers throw with their hand, not their foot.
(just kidding)
Actually, under Fed (high school) rules if the pitcher is in the wind up position he must step off the rubber (pivot foot first) before throwing to a base.
Under OBR (Official Baseball Rules) a pitcher in the wind up position is not required to step off first. From the rubber he may step toward and throw to a base in an attempt to pick off a runner.