Arabians are my breed of choice. Although this is a beautiful horse (they all are!), I don't find him to be either show-quality or stallion-quality. He should be a gelding. From reading the caption below the video, "This video shows how professional show-training influences a horse so that even after a period of 15 years without that, certain triggers can cause a rapid change in mood and behaviour. The first part of the video shows how nice and friendly the stallion behaves, and then towards the end you can realize the rapid change due to the whip," I get the impression this is an older horse (over 15 yrs old anyway) that has not been faced with "training" in over 15 years, yet he is still easily rattled by popular "training" methods. And yes, he is somewhat stiff, perhaps from an old lameness or injury.
Popular training for Arabians was to irritate them just prior to entering the show ring in order to add a little umph! to their movement, putting them on high alert- head, ears and tail up, eyes wide, nostrils flared, a little bounce to their step. An Arabian of good breeding would show these qualities naturally, IMO, and need no irritation.
Regardless, I think this woman's video shows little beyond her inability to properly handle a horse.
Several times I see her put herself in dangerous positions and do lazy, irresponsible things that certainly could result in injury. If nothing else, this video shows a stallion of excellent temperament. She states that he gets highly irritated and responds.... well, duh, she's irritating him! Probably has nothing to do with any previous training! Heck, I'd bite at her too if she kept poking and swiping me. Stallions tend to be "mouthy" as this one shows, and that has nothing to do with training (unless it gets out of hand and becomes a vice) and has everything to do with hormones and nature. And even then, the stallion really is quite even-tempered, all things considered.
Alas, someone has touched a nerve! I could go on for days... but I won't.