I've met a dozen beginner/intermediate players who refuse to take any feedback or instruction at all because they're convinced they know better. And it's not all because they took lessons from a particular instructor.Classics or Sams. Take your pick. Ill play you for free, I dont care. Hell, Ill even buy you a beer and pay for the table time.
There was another student of your instructor on this very forum some time back.
https://forums.azbilliards.com/member.php?u=91462
The local retailer sold him $2000+ worth of equipment, and he had lessons for almost 2 years IIRC. He also had a complete lack of fundamentals, and a chicken wing that would make Colonel Sanders jealous. AFTER LOTS OF LESSONS. 'Banks' another member from this forum and myself tried to help the kid in person, but he felt he knew better too, because his instructor filled his head full of horseshit.
...
This device seems perfect for people like that. It's easy to disagree with somebody (an instructor, a more experienced player, etc.) because you think you know better.
How are they going to argue with a mechanical/electronic device that's measuring their stroke objectively?
So, rather than this device being a thing that bilks them out of more money, it seems to me like the only viable option for improving their game.