Kinda worthless vid because as they explain around 18:00, that the power cuts out around 16 mph, then it's entirely manpowered. And these guys are pretty fit road cyclists. They'd have done this route faster with a decent road bike.
This experiment would have actual value if either a) they used 28 mph ebikes, or b) had riders for whom riding 16 mph on a comparable manual bike is out of reach.
If you can cruise at 17-20 mph on a manual bike, an ebike with a 15-20 mph limit is probably a waste of money and effort, unless you've got lots of hills, wind, cargo or heat to deal with.