That's a very interesting point of view, but it doesn't quite mesh with my view of the world. I think it makes perfect sense for modules much smaller than "packages big enough to be submitted to a package manager" to have small, well-defined APIs. I'm not sure why thoughtfully limiting APIs would be a good thing at the package level but a bad thing at the module level.
Seems like there's a good case to be made for a 3rd level of visibility between private and public. Similar to Java's package level. I'd like to see (from least to most public):
private: only visible inside the current namespace/module
crate (possible name): importable anywhere in the current crate/compilation unit
public: visible outside the crate/compilation unit
