If I were to guess today, I'd say that my front wheel was within about 2 meters or so of the tail gate.
This is obviously dangerous, but the truck was going slow; slow enough that if it slammed on the brakes, I would have been able to react (and failing that, not get badly hurt).
It was a strange sensation. It took effort to pedal up to the tailgate, but then you feel the effort drop off, as if you went over an invisible ridge.
I think the article must have ignored drag, which makes their estimate of 35-40 mpg unrealistic. Tour de France sprinters can reach 45mph speed, but the average Tour speed is more like 25-30 mph. Running is less efficient, and less aerodynamic, than cycling.
I think that used to be true in the early wave of e-bikes.
Today, I regularly see e-bikes and scooters easily keeping up with traffic that is moving upward of 50 km/h.
If there are still e-things on the market today with speed limitations not related to their power capacity, people must be easily working around those limits somehow, with firmware patches or secret codes or what have you.
Most of the stuff comes from China, which is an uncontrollable entity that doesn't care about regulations in North America and elsewhere.