This thread is marked solved. I am still intrigued by the problem, and, after extensive googling, which only led to countless repeats by various media, of exactly the same content, this was the best I could come up with. Take it or leave it
"Microsoft also states that reports that Windows 10 being forced on users are “not accurate” and suggests that users who seeing Windows 10 installed unexpectedly might have pre-selected to upgrade to the new operating system.
A Microsoft spokesperson said in a Q&A: “We have updated the upgrade experience for some of our customers, who had previously reserved their upgrade, to schedule a time for their upgrade to take place.”
Users may have also have unwittingly clicked or tapped on the ‘accept’ or ‘OK’ button, which user interface elements such as Windows Access Control and the modern trend of extensive permissions and password requests bombarding users with pop-ups demanding action, has trained users to do."