I would also suggest SonicMojo should take up umpiring since it is so easy to see illegal pitches. (Clue: It’s not always.)
Indeed I will concede I should have limited my comments to this situation, as this is what I had in mind when commenting, not all varieties of illegal pitches. As defined by NFHS, this is a crow hop. Period. No slow motion needed. The push knee only points back and flexes if the pitcher has crow hopped.