That's a completely worthless figure of merit (I assume he means thrust to weight; because electric helicopters have abysmal power to weight ratio -shit like this matters) and no reason to believe in this nonsense. By the same reasoning, one could build a piston engined supersonic aircraft because there are piston engined helicopters. Another thing that has a high thrust to weight ratio; those water rockets I used to play with as a kid.[0] Pretty sure you can't go supersonic with those either unless you fire them out of a howitzer.
Electric airplanes are a terrible idea without battery technology comparable to hydrocarbon power to weight ratios. Even then, they're a terrible idea unless the motivating technology is lighter than a jet engine and tanks for reasons that should be obvious to anyone with high school physics educations.