That's a sign of how accepted it has become to say that you can't find any local workers that know Python when filling out the H1-B forms. The requirement is there but it's normally overlooked.

"The intent of the H-1B provisions is to help employers who cannot otherwise obtain needed business skills and abilities from the U.S. workforce [...]"

https://www.dol.gov/agencies/whd/immigration/h1b

At some point it becomes “couldn’t obtain the required talent at the prices the business was willing to pay”.