AlexS, I was & still am a supporter of PNH's principles of horsemanship (easily accessed in his book) & foundation Levels 1 & 2, after a few misdirectives given by Linda are corrected (sit heavy to back up, etc.)
I've found that the classical teachers teach differently than Linda is teaching the dressage, that there seems to be a communication breakdown between Walter Zettl & the Parellis, because he IS qualified, as well as the qualified teachers who worked with her at their dressage summit. She claims to have had the epiphany about what "contact" is, & they don't say boo (look at a video of Nuno Oliveira riding - he needed Linda to show him about contact?) & she's teaching explicit rider-position stuff, involving clenching major muscle groups, that differs with classical.
I see that classical is correct, it extends the lives of horses & makes them happy, & even the Mongols & American Indians didn't need Linda to show them anything.
Pat, to his credit, never claimed to be revolutionizing any part of true horsemanship: he always said his way is vaquero horsemanship & "natural hms is so old it's new again". I feel that Pat needed to have remained the chief of the outfit.
To add to the problems in PNH, I learned over the years that Pat has what I call "loose screw moments" coupled with cover-up stories: his trailer-load of the horse that escaped out of the trailer whilst Pat was schmoozing with his female owner, his being over-horsed with Catwalk, his holding the rein taut & causing Troubador to go into a spin then a buck at contest, throwing Pat (& Pat saying that it was a voluntary dismount). The loose screw moments happen rarely, thus it isn't fair to say that he's a lousy horseman; nevertheless, it's stressful when one's teacher has those moments.
Then, there's the intimidation & $ corruption described by OP, as well as the high-end merchandise & hugs sums required to try & carve out a career as an instructor. OP, after spending thousands, surely shouldn't've been treated as she was, for simply piping up that the course didn't deliver, e.g.
So, yes, the principals found in the book & most of L1-2 are great! :)
Eta: I do see the anxious look in Pat's face there with Catwalk; that says that Pat was over-horsed with Catwalk; a picture's worth a thousand words.