I work my ranch horses barefoot. I have not used hoof boots, but have taken hobby riders with me to check cows and the boots either A) malfunctioned in someway, or B) rubbed the horses and made them sore. Our pastures are a mix of grasses, low brush, rock, small treed areas, flats, hills and draws.
I was not impressed and it interfered with caring for the cattle. I will no longer take anyone out that uses them.
Perhaps these peoples' horses were not in decent condition and that was enough to make their gait ineffective. Or they weren't muscled enough to maintain balance over the varying terrain.