Hmmm it's almost like saddlebreds have a genetic predisposition to developing swaybacks and other ligament lasticity disorders with age or something.
No swaybacks are not linked to riding. Horses are born with a predisposition to developing a swayback as they age.
Swaybacks can have a genetic component, and its common for it to be hereditary in saddlebreds. But bad posture, which as I'm sure you know is common in saddleseat riding from the restricted heads and shoulders, saddle placed too far back, high heels & long/low toes, neck tension from being ridden in absolute elevation, etc., is also a cause and exacerbator of swayback. I don't think OP is wrong in this case tbh. There are likely a combo of factors causing the extreme swayback of this horse, including bad riding (or bad training in draw reins on the lunge in preparation for riding) at a young age.
I think the QH racehorse Corona Cartel and his offspring present an interesting study on swaybacks. There definitely seems to be a genetic predisposition for it with him. He had it and so do many of his progeny. But which ones had it worse? The ones racing at 2 or the ones started later? I personally don't know Corona Cartel racehorses with swayback, but I've seen plenty online. I have personally known several horses by Corona Cartel bred for barrels, started at 3, and used for general riding, and they either never developed swaybacks or developed it in old age and too a lesser degree than their racing siblings.
