Michael Black wrote:

You'd have to go back many decades before you hit a point where
a large percentage of shortwave receivers were regenerative. Go
back forty, and some would be regenerative, albeit they'd be at
the low cost end of the spectrum. Go back to the thirties, and
regeneration likely was still common, because superheterodyne designs
used more components and hence were too costly for many in the depression
era.

Nope, nearly all radios by the early 1930's were superhet.