Yes, that's actually true when you backup your PC Documents folder with OneDrive. If you really want to stop OneDrive from syncing your files (Desktop, Documents, and Pictures folder) then Unlink your account from OneDrive settings but before doing that, make sure to enable the option "Always keep on this device" for all your files:
- Open the Documents folder.
- Select all files and folders in it (or press Ctrl + A in your keyboard)
- Hover your mouse in any of these selected files, right-click and select "Always keep on this device"
- Wait until the status icons for all selected files turn from white to green icons.
- Do the same steps for your files in Desktop and Pictures folder, if they are also synced on OneDrive.
To unlink OneDrive from your PC:
https://www.tenforums.com/tutorials/36246-link-...
Note: This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.