I know nothing about such dogs or farms, but why would he allow the dog to go beyond the property fence, even though it was still his property? Why include that on the limits of the property that takes 1 to 2 years to teach?
We had one dog growing up that liked to commune with a particular herd of cattle (in a friendly way) in a distant field on occasion, and nobody and nothing could stop it when it had that inclination. Dog on a mission.
Dogs are smart and learn outer boundaries and roam looking for predators, stock are kept bounded and once an area is cropped (to some degree) they are moved to another grazing area.