Here's my take on it:
- HB makes a quick step to the side and stops: false start.
- HB makes a quick step to the side and continues to go in motion parallel to the LOS after a very very brief pause: illegal shift.
- HB makes a quick step forward: false start.
- HB makes a quick step forward and corrects himself to going parallel LOS: false start.
In 1, 3, and 4, the HB is presumed to have missed the snap count.
In 2, though, this is a very common way for a lot of teams up here to go into motion. We see it on a weekly basis, especially in 9-man games, from nearly every back. Very sharp, crisp, quick moves to begin their motion.