The key point is that loaders should be using the spec, not any of the module attrs (like `__file__` and `__cached__`), nor setting them.

For the specific paragraph I referenced, it would look more like:

  It is also appropriate to set __cached__ when __file__ is not set.
  However, that scenario is quite atypical.  Ultimately, __file__ and
  __cached__ are set by the import system from the module spec provided
  by the finder.  The spec instructs the loader.  If a loader can load
  from a cached module but otherwise does not load from a file, that
  atypical scenario may be appropriate.