That's fascinating, is this explained in detail somewhere? How did you learn about this?

I'm learning ASL. That led me to learn about Deaf culture in North America. The stories that the Deaf have told each other, and have passed down. A world where everyone is deaf is one of the first stories you'll learn about; I'm not even sure when I first encountered it, but it was in that context.

One common modern version of the fable is told with an astronaut who finds that they've landed on a parallel Earth where everyone is Deaf and sign language is the norm.

The book A Study of American Deaf Folklore by Susan D Rutherford is a bit dated now but interesting in exploring the functions and roles of myths here.