Darn it! That's what I get for hurrying.
After downloading the Sonoma 17.1 update, after completion, a couple of windows I hadn't seen before popped up.
I'm used to the usual "setting up your preferences window" and a few others but this time there was also a different window requiring me to sign in to iCloud with my Apple ID Password. Being in a bit of a hurry I typed it in and hit return. It was just as the window was about to wink out I realised there was also a pre-filled tick box saying, "Sync your Documents and Desktop Folders to iCloud". aaaargggg!
Now I have studiously avoided storing my Desktop and Documents folders in iCloud since the option became available and let me make it clear right now, Syncing your Documents and Desktop Folders to iCloud is not the same as storing them there was. In the older option of storing them (to save space) they were removed from your HD and uploaded to iCloud Drive where they could be accessed or downloaded. The sync option simply makes them available on all of your devices as well as providing a backup of sorts.
From my point of view this has just used up a lot of iCloud Drive storage without changing anything on my MBP. All of the files are still on my HD but now (if I wanted) I could download them onto my iPhone/iPad as well.
Of course if I'd had my wits about me at the time I would have unticked that box. It really peeves me that Apple pre-tick that box and the Store my Documents and Desktop Files in iCloud option at device setup as if it's a given that users will want that, meaning you have to look for it and un-tick it every time. Encryption is the same although not so much of a big deal as it used to be.
Anyway, it can be undone and luckily for me we have iCloud + with 2TB of shared storage so we still have nearly 1TB free but others may not be so lucky.
