It doesn't speak to the technical difficulty, but his example, and all of yours, help put the distance into context that we can intuitively understand. It's definitely helpful.
The kinetic energy of 1 kg moving at orbital velocity is about 31 megajoules. The potential energy of the same kilogram suspended 100km overhead is less than a megajoule.
Most of the difficulty to orbit isn't distance, it's the amount of energy it takes to get something moving that fast.
Actually it's much, much worse than that, because it's actually the change in momentum involved.
The point is it's less far than it looks (humans are bad at judging vertical distances), and giving a real-world comparison makes the real height easier to conceptualize than an abstract number.
Humans are also bad at comparing horizontal differences to vertical ones. Switching from one to the other obscures the difficulty of going higher. If the peak of Everest were 8,848 meters in distance rather than height, it would be an unremarkable hike.
That makes sense; it's easier to take a horizontal step than a vertical one. Someone should do up an infographic showing the effect of gravity on work required for horizontal versus vertical movement.
At 21,000 meters, the U-2 didn't fly that high. That's only a half marathon, and many people can run that distance easily.
In other words, I fail to understand your point, even omitting the 7.9km/second sideways velocity for LEO.