I think what they mean is: if you see a line like `import git.example.com/foo/bar/baz`, that could be package `baz` inside module `git.example.com/foo/bar`, or it could be package `bar/baz` inside module `git.example.com/foo`.

Also, even if you know it's the latter, package namespacing isn't strictly related to directory structure, so `bar/baz` has no specific meaning outside of the context of a go import. They could have used any other separator for package components - `git.example.com/foo:bar:baz` - but instead they chose the slash, making the scheme both technically ambiguous and easy to confuse for an HTTP URL.