This may be more of a feature request than a bug report, but there are two points regarding the permissions for Administrator users that might need addressing:
- Although the first Administrator user is automatically a member of all of the initial user groups (except Parents & Guardians, per Issue #1737298: Parents & Guardians has a different owner than the other out-of-the-box user groups), after that, all other Administrator users are not automatically members of all user groups. If a site has more than one Administrator account creating user groups, that could get cumbersome, when it comes to administering membership or menus for those user groups.
- On a related note, I anticipated that Administrators would have administrative access to every user group they belong to, but that's not the case. Just like Authenticated users or Content Creators, Administrator users have to be an Administrator Member of the user group (or they have to have created the user group in the first place) to have access to the group's admin menus. I'm not sure if that's necessarily something that needs to be "fixed," but it ran counter to my expectations, so I thought I'd check anyway.