> had deployed Elixir in a way that broke the BEAM (which he viewed as "old and deprecated")

I'd love to hear more about this!

> instead of using private functions as they're intended—created a pattern of SomePublicModule and SomePublicModule.Private, where he placed all the "private" functions in the SomePublicModule.Private module as public functions so that he could "test them."

Yeah, this is weird; you can just put your tests in the PublicModule. Or you can just solve this by not testing your private code ;)