Well -- Loved one -- I'll bet you have actually 'fixed' as many truly herd-bound horses like this as you have seen Thorobreds being abused in cross ties on the race track. [I am afraid you lost ALL credibility with me on that one!]
You can spout all of the theories you want, but horses that get this panicked over separation have probably not seen the Parelli DVDs. A horse like this is as dangerous as an aggressive horse. I, personally, would not be bothered taking my time and risking my well-being even trying to work with a horse like this until it has gotten over the separation. It has nothing about the horse's relationship with its owner and has everything to do with the fact that the horse has gotten phobic and irrational about a 'horse friendship'.
As a matter of fact, I had one brought to me a few years ago by a woman that was 100% into Parelli and had had years of private tutoring by a 3 star (or something like that) Parelli instructor. She just could not understand why her perfectly trained horse that knew all 7 games and would do them at liberty had suddenly come completely apart on her when she moved him. It seems he 'fell in love' with a mare at the new place she had him and he went completely crazy. It was not her relationship but his mind-set that needed changed.
We inherited the worst one I have ever seen when my husband went to work for a cutting horse breeder. He had a mare that had won quite a bit of money as a 3 and 4 year old and was hauled all over the Midwest. She came back to live home as a 5 year old and was going to be shown in non-pro by her owner. Then, she fell in love with the horses on either side of her stall. She was home where the man had open stall tops with mesh instead of solid sides like his trainer had. We put her in a solid stud stall and she ruined the stall, dug holes and grooves in the floor a foot or deeper, sored up both hocks twisting and turning on them -- so she was put back in her open stall.
She was hauled to a cutting show in St Louis and quit the cow to whinny in the middle of a class. This, mind you, is a very well trained finished cutting mare that lost her mind. She reared up in the warm-up pen with her non-pro owner. She was un-showable and the owner was beside himself as he had over $20,000.00 in training in her and she had shown that she could win a pretty tough cutting.
I told them I thought tying her out would be the only solution. [I was training for the public out of the same barn.] The owner OKed it, so we found a suitable tree about 100 yards from the barn. We hung a good rope down from a big tree limb (had to get in a tractor front end loader to do it). It took 3 full days for her to give it up. The first day, husband had to go out with the front end loader 2 or 3 times and fill back in the hole she dug. It was about 3 feet deep and she was standing on her tippy-toes. He only had to fill it back up once the second day and by the afternoon of the third day, she was standing with a hip cocked by that evening.
They went back to riding her the next day and she was a different horse. They left the rope hanging from the tree and tied her out to it to cool off after each bath following working -- just to make sure she kept her thinking straight. They started hauling her again shortly after that and she rode like she was supposed to. They even took her to overnight shows and she was OK in a strange barn with strange horses. The only thing they did differently with her was to change her stall and/or her neighbors regularly so sh ewould not get that attached to a certain horse after that.