Pretty sure that's with totally unobstructed, pure air between the goggles and the drone, 10km away. And, the pilots head was constantly make small adjustments turning left and right to maximize the signal reception.
As others have reported, real-world range with tree, buildings, other human bags-of-mostly-water (Star Trek reference, key point is water is one of the best absorbers of RF radiation), hills, mountains, and on and on in the way, it's about 1-2km.
Which really is only needed for excursions like the "Flight of the Year"...