It's more likely remote controlled. There's probably a guy with a controller near by. They've been around for a couple of decades now, but are generally only used where an angle is too steep or too close to a highway or cliff face.
I don't get it, don't you guys have a lawn bot at home? Who in their right mind would mow their lawn by hand these days? Sure, this is scaled up by a considerate amount, but its the same technology (though I imagine this boy uses beacons for navigation as opposed to gps or wire).
We have 1 1/2 acres. Mowing it by hand, even with a self-propelled mower, sucks. Especially in August. If we could afford a lawn bot, we'd definitely get one.