Yeah, I think it's ridiculous. Supposedly they already have people watching warm up rings in Germany due to a ban of it there at competitions. Feel free to correct me though if I'm wrong.
Asking the horse to preform such an unnatural movement is obsurd. The horse is physically incapable of using it's hinds correctly while doing rollkur, and it is not a 'correct' form of riding, therefore there is no correct/incorrect way to do it, the whole idea of it, is incorrect.
Research has proven, that the way the horse curls under, actually does not stretch any of the muscles at all, but just pulls the ligaments. The horses have to use their under neck muscle to pull their nose in and defy gravity