Here is my understanding on this. As we see there are Three options
1. No, set as private
2. Admins only
Option 1:If you keep that option as Private it means that when you upload the file it will be visible to you only and no one else. Also it means that if you don’t access once every 48 hours file will be removed by the system and you won’t be able to run the action as an admin from actions command
Option 2: Only Admins will be able to access the default file of an Import if they don’t upload their own file. Meaning admins will be able to run the action
Option 3: Everyone will be able to access the default file of an import if they don’t upload their own file.