Managers in category show up as markers (in allocation)

When allocation markers in an assignment, all moodle managers on category and system level show up in the drop-down along with the teachers in the course.

If I remove the roles permission to mark, mod/assign:grade, the Mananger role cannot even open the submissions view which is necessary to be able to support the teachers.

Is this a bug, or just me having change some other permission?

Using Moodle 2.6.3