It's amazing what horses and riders can learn to do. I wonder how much harder it would be to do that kind of stuff in a western saddle and with no training for horse and rider? But then again, when you're riding for your life, it would be a real motivating factor.
I remember seeing a cross country three-day event jumping obstacle that I can't find on line. It was called an Italian grave, if I remember correctly after 40 plus years. It consisted of a high two-layered earth platform with a a water obstacle on both sides and a high rail jump in the center with almost no take off or landing area. I don't know how a mortal horse or rider could get over it, but at the Maryland Equestrian center cross country riders, including, I recall, the Olympic team, trained on it. I was in awe.