The difference between backup/mirror and move

The terminology used by Microsoft to describe what OneDrive does is seriously flawed.

To most people, the concept of backup means duplicating files to another location or archive file. That is a backup provides a mirror copy of files being backed up.

OneDrive doesn't backup or mirror files, it moves them to the cloud. They are no longer available offline.

You can of course disable syncing which is also wrong terminology because files are not synced, they're moved, which is a copy operation followed by a delete.

No problem. You can turn off folder/file syncing and copy the relevant folders/files to your hard drive so they're accessible offline. I then uninstalled OneDrive to make certain.

The trouble is, a few days ago my Outlook 365 broke because of a webview2 error which made editing drafts unusable. No problem, I did a repair which didn't fix it, and finally uninstalled office and reinstalled. 

When I reinstalled office, it also reinstalled OneDrive with the default settings, so OneDrive promptly reenabled folder redirection and the files/folders on the local drive disappeared. 12 months' worth of email, a bunch of documents, gone.

No file date/time check to determine the direction of synchronization so that newer files replaced older files, no intelligence whatsoever. I won't quote what I said when I found out because there might be ladies present.

Luckily my email service uses MAPI so some time in the future I'll have my emails back, I hope. But updated and new files are gone.

Did I have a current backup? I did until someone borrowed my backup drive for something they thought was more important. It wouldn't have mattered if OneDrive had left the newer file copies alone, but the files on OneDrive had all the old date/time stamps from when I turned OneDrive off and that was it.

Then there are the little things like if folder redirection was done properly so even the command prompt was appropriately redirected. Not so with OneDrive. Amateur.

Backup should not mean my files are moved so there is only a single copy left, ditto with synchronization.

So not only is the wrong terminology used, but the implementation of OneDrive also has major room for improvement which may never happen.

I also have a MacBook Pro and while I'm much more conversant with Windows, Mark Russinivich's Sysinterbals tools etc, and have done extensive Windows application debugging. I would hope my experience is simply due to ignorance about OneDrive, but I that must be true for a lot of people. It's far from foolproof.