Yes it has been done for reining, but I have NEVER seen it in Dressasge especially not with the horse that happy.
But also note that the horse in that video that you posted , nrhareiner, there are many times the horse tosses his tail which is a sign of uphappiness, too strong of cues, or protest.
The dressage video: 7 swishes...normally at lead changes which could mean that she's asking a bit too hard
Reining: I see 10+ swishes in a video that was technically only half the length of the other, THEN when the girl got off to grab the gun I saw a horse with no trust in his rider as he ran behind her
Why is it that some people can't accept that training like that has been going on long before Parelli?
Yes it has gone long before Parelli, but the dressage rider had a happier horse ;) and a happy horse is what is important to me and should be for everyone