In general, movement along the target line does not concern me. For example, in the wind up, a rock back before coming forward can have its benefit. I try to mostly discourage rotational movement around the target line such as rotating toward second base during the lift.
I agree about the rearward movement from the stretch. While it may help with getting your movement going toward home, it delays your delivery to the plate. Tenths of seconds count in the running game. Since, I'll bet your pick off does not start with that rock backward, it may help runners time their jump. If your feet are closer together it can help with your jump turn to first base.
I found it beneficial to have more than one stretch delivery and I would mix it up in action counts to make it harder for the runner to know when to start his secondary lead or to get a good jump. This delivery may not be representative of how your pitch from the stretch in those situations.
Most of what I see from this angle is pretty good. The home plate angle will give us more on your posture, alignment, etc.