The popular oscilloscope's 20 MHz BW limit ...

[alm]

In the US, Tektronix market share for oscilloscopes might have been about 85% and HP, who was watching Tektronix closely, 10% around that time [1]. So it does not sound that far-fetched to me that a single Tektronix designer might have defined a standard.

[1] Logic State Analyzers Birthing Pains, Chuck House, page 34

[oldway]

There are other examples of standards established by technical limitations:

The 20K/V sensitivity of analog multimeters is one of them.

Even if 100K/V analog multimeters could be made, they were fragile and difficult to manufacture.

A 20K/V multimeter was the best solution of good sensitivity (galvanometer of 50 µA) and of good robustness ... it became a standard and all the measurements indicated on the diagrams of the time specify that they are made with a 20K/V multimeter.