Matters of law aside, this is not a valid training technique. Flexibility takes time and effort to develop. Pushing beyond what is reasonable causes injury. Injury delays development or worse. If a coach does not know this very simple fact, they should not be coaching. We don't ask people to lift more than they can safely handle for the same reason. It's important to challenge yourself, but you also need to know when to stop. Intense pain is an obvious sign that you aren't ready to do what you are trying to do. It's insane that any adult would encourage obvious pain and have others participate in inflicting it. This is not just poor judgement; it is deliberate abuse.