I had been crossing off the upgrade but a few days ago it started to upgrade without my sayso, admittedly after it had warned me with an intermittent countdown. I pulled the plug on it, literally, and I started it again on W7 and is has not tried it again.
I tried
and it cleared the flag after a restart.
I feel that my W7 is now running a lot faster without 9 gigs of W10 lurking in the background.