I ended up writing up more thoughts on this in the issue about __package__: https://bugs.python.org/issue45540#msg404619.

Users can call importlib.util.find_spec(), which is probably good enough to figure out how a module was originally imported.  So I don't have any serious objections to making the spec the writable single-source-of-truth.

FWIW, I'd rather there were high-level helpers available as an alternative to the low-level practice of modifying module attrs.  However, in this case it probably isn't frequent enough to make it worth it.