A Microsoft file hosting and synchronization service.
Is your Downloads folder in your OneDrive folder? Your Downloads folder is not a folder to select in Manage Backup, so somehow you have been moving folders from their default locations.
Does that matter? You seem more concerned about trying to identify something I’ve done wrong rather than trying to help. As I’ve said, I’ve had OneDrive on a secondary drive for years, and yes probably Downloads has been there as it sits with the core Documents, Desktop, Pictures, Videos folders.
Yes, I’ve contacted Ms support but having used them before I have 0% confidence in them helping.