Yeah, that’s always the discussion when writing a Python utility that has a unix equivalent: do you want to be familiar to Python users or to the unix tool users?

I don’t have a strong opinion.  I think unix users would have no reason to use python -m tarfile, and windows users won’t have the expectation that the interface is the same as tar—unless they are unix people who are using a windows machine for whatever reason.  If it were me, I’d just start with python -m tarfile --help, so I’d have no expectations :)