I don't know this guy ( Certified Pitching Instructor ) but I see that he is a Tincher certified instructor in the Raleigh area.
My dd sees Denny a 2-3 times a year and I can tell you he advocates IR (IMO, boardmember and the new javasource videos explain it better). I can also tell you Denny teaches drive mechanics similar to javasource.
I'm not aware that any Tincher instructors post or lurk here, so I doubt they have heard the term "IR", but the ones I've seen in clinics promote it.
FWIW, several DFP-ers take their dd to Tincher instructors and I have yet to see a negative post about any of them.
I'm in Raleigh, and there aren't that many known private coaches here, either hitting or pitching, compared to metro Atlanta, where we lived previously. Hard to find a good one.
My DD is not a pitcher, so I'm particularly ignorant of pitching coaches. But I do know that the head coach at Meredith College teaches private lessons and was an outstanding pitcher at a D-1 school. That doesn't guarantee that she teaches IR, but if my daughter was a pitcher, I might start there. Her name is Kim Scavone.