In answer to your question CC,about English diciplines, I’m only familiar with two trainers bringing up babies. One racing and one ASB show horses. The race guy did it as a sideline (actually his job supported his training biz but . . .) and he just didn’t have the time.
He even said so, a couple of years ago when he backed two fillies and they were in essence feral. He hadn’t had the time to play with them and make them used to being handled, nor was it of importance to him. He really didn’t see farther down the line to the fillies’ future careers, apart from as broodmares.
The colt had been backed the previous year and had had more time - that colt was a biter, and very smart, I recall holding him at the wash rack (which is just what they do, never saw any other racehorse tied fast and I think it is a question of protecting your asset to the nth degree) and he opened his mouth waaaay up and made to bite at the trainer, testing you see, and he did get a pop and a growl. I was acting as groom so a great deal of training in ground manners comes from the groom, which includes getting poked with a fork handle or swatted back with a towel if they are restless during stall cleaning. Some grooms are truly horsemen and others . . . not so much.
The trainer guy would tie the colt fast to the back of the stall but move the fillies to an empty stall down the shedrow. I remember I came late to watch a race and trainer hadn’t gotten anybody to groom at the race, I couldn’t get into the enclosure by then and it was quite the little rodeo to get the jockey up - you see at the barn the trainer had always found a good corner to wedge the colt in for mounting, well, you are expected to mount out in the circle at this track.
Did the trainer change his methods? No. He figured he was one man alone and it fit with his schedule to use the wall at the barn rather than try to get someone to hold, or tie the horse’s head when that would have just been 180 degrees of possible movement. They are young. Too young in my book, I think John Shirrif and the Mosses did a spectacular thing letting Zenyatta wait - she just wasn’t ready and she is still one with a lot of excess energy.
The ASB’s are just now turning three and are being worked. They are expected to stand tied, but only in the stall, they are supervised when in cross ties. They are expected to come out of the stall and into the show ring with flash, fire and brilliance.
The old guy was a lower level competitor - his ground manners leave a lot to be desired but under saddle or in the lines he behaves beautifully, up in the bridle, still has hock action at 24 years old, but the first day we brought him up from grass he basically plowed over my instructor in the stall, walking, worrying, pawing - heck he was walking and pawing in the arena.
He’s been with me a year and has learned better manners in hand - but there is no reward in the ASB world for quiet - even the BOD of the breed organization chides the members for bringing horses in who bounce all over the arena during the strip for conformation, but they do win even if “manners” are judged - gracious, I’ve seen a gorgeous horse sweep the ribbons at a charity show, a junior’s horse, and that mare looked to be ready to break and run for the far horizons the whole time, barely keeping a straight line, snorting, eyes white. Manners are supposed to be paramount for juniors’ and ladies’ horses, but pretty and head turning get marked higher than dull and sensible.
So these are some of the reasons I guess, why some trainers, and there are Western ones out there too, my mare was sold to me Western and one of my good friends bought a little barrel horse who was he!! on four legs, put “performance” first and ability to be a sensible working horse second.