I checked https://docs.python.org/3/library/dis.html and there is no mention of dis having a command-line interface.  This suggests that _test is likely present only for testing the module, not for using it.  This was common a couple of decades ago before we had unittests.  If _test were considered obsolete, it could be removed.

By suggesting that the command line interface by upgraded, I suspect that you are implicitly suggesting that it be considered 'official'.  If so, that '_test' should become '_main' (where the underscore leaves it out of __all__), and the CLI documented as in other modules with a CLI.  (I am not up on the details and policy around this issue.)

It may be appropriate to start a discussion of python-ideas.