By default when you use WP CLI it will assign the post to the default language.
So for example if I have Norsk and Finish and Norsk is set as default, if I run this command: wp post create --post-content="test" --post_status="publish" --post_title="test" I expect the post to be assigned to Norsk language.
But when I activate the Polylang-CLI package then when I use standard WP CLI the post is no longer assigned to the default language.
In my opinion the expected behaviour should be that a 3rd party package should not affect the standard WP CLI in any way.