von Ken Task.
To my way of thinking: Moodle is a shared resource. One teacher/user should not use more than their 'fair share' of space - but how does one define that? How much privacy should users have when it comes to files? Always debatable!
Am in agreement with you, an Admin level user should be able to see all - do all.
There is a plugin that will help with backup files:
https://moodle.org/plugins/report_allbackups
Discovered many moons ago that making command line queries of tables - like mdl_files, mdl_courses, mdl_users - dumped to text files an admin level user could see things not seen in the GUI.
My 2 cents!
'SoS', Ken