Perhaps I didn't read the fine print, but my win 10 PC started doing this without notification.
What really pissed me off is that any files in odt were deleted and not transferred at all, as were some pdf's - only macrorshaft office files were uploaded.
So if I hadn't been backing up all my files regularly to an external hdd, hundreds of hours of work on my family history would have been lost. As it was, I had to get some copies from my sister to who I had given them, and some had to be re-created from the remaining pdf's.
So, lesson learned - all documents, downloads, photos etc are on separate disks to "drive C", and I continue to back up regularly. - fuck you macroshaft.
Why am I using win instead of unbuntu? Very good question that I've asked myself several times since then.