Thanks Iñaki for checking the code, and thanks Caitlyn for mentioning documenting the behaviour.
I think the current behaviour is a bug and have reported it as MDL-61236. I've also added a note about it to the documentation pages Self enrolment and Enrolment FAQ.
Regarding who does documentation updates, everyone is welcome to help! You can log in to Moodle Docs with your moodle.org username and password then edit pages.