Notably absent from the list of changes in iOS 8.1 is a fix for the Reset All Settings Including iCloud Drive Data bug.

Whoops.

I can imagine what they did, and it's kind of funny. You reset all settings, that deletes the files, the device is bound to iCloud even after the reboot (activation lock!) and then on first boot the sync gadget says "Oh hey, no files." and promptly ... syncs that.

At least, that's my totally unsubstantiated guess as to the cause, given that it's taking so long to fix. It'll be interesting to know what the problem was ... someday, when someone feels brave enough to talk about it.