> It’s not clear that such speeds are actually capable on stock parts from nearly any electric bicycle, and legal electric bikes are not capable of exceeding either 20 or 28 mph, depending on their classification,

It's like the author did zero research.

While you can't easily modify most bikes to hit 70mph, there is an entire market segment of "class 2" "ebikes" than can be trivially modified to reach speeds that significantly exceed what the law allows (and arguably what is safe on those hardware components.) Often this can be done in the software without any hardware modification. If it can't, there are usually simple modifications that can be made to achieve the same thing.