When you think about it minute, teacher is doing the 'right' thing ... major assignment or work done, make a course backup. That's a good safe practice. What teachers don't really understand is Moodle is a shared resource.
Have a teacher on one K12 system that teaches a Digital/Multimedia course. Assignments are always large ... file wise. After major assignments were due, teacher made a course backup, but didn't erase/remove older backups. Eventually course got to 139 Gig. Couldn't run autobackups. And when a 1TB data got to 95% full before the end of an Academic calendar year (teacher had 6 older backups) with the Videos portion of this course yet to come, finally had to say something. It did take 'peer pressure' for this teacher to adjust a little.
Was prepared to pull the trigger on moosh scripts if teacher didn't adjust ... for the good of all teachers/students in the system. Since am a remote admin and not a member of that faculty/IT department they could always 'fire me' - but that would mean internal IT folks would have to become admins.
'spirit of sharing', Ken