I couldn't see the pitching plate, but using second base, I drew some lines for reference. Obviously this is only an estimation. If it is as I see it, I hope I would have noticed it and called the illegal pitch.
(Unless of course there was a bunch of coaches and parents behind me, whining, calling UICs over and taking video of it... then I would probably "realize" it was so borderline that there was no need to call it.
)
From the video, I would agree with others that it appears the top part of the step has a swing of the foot out slightly and then back in.
