Hmm.  I think that chapter could use a more extensive rewrite with some additional information provided.  For example, you actually can have a __main__ module in a package, and anything inside it will execute when the package is run via -m.

The "otherwise anonymous" is a bit misleading, I think.  The real distinction is that when a module is run as a script, __name__ is set to __main__, whereas when it is imported, __name__ is the module name.  This distinction allows a module to easily detect when it is being run as a script rather than imported, and the "idiomatic 'conditional script' stanza" is how to implement the behavior of a module conditionally acting as a script depending on how it is accessed.