No, that's explicitly not how MS updates worked: up to now, they were updates to existing OS, not automatic reinstall.
If I don't want it, I don't get asked if I want it: 19:00 there was a working Win7 box, 07:00 next day, there was a broken steaming pile of something, apparently Windows 10. No prompts, full auto.
Program files: deleted. Users folder: moved into some other location (both). I don't give a flying fork if that was intentional, it should not have happened, full stop.
In other words, FU, astroturfer. Take your piece of crap and shove it. (Yes, your wonderful Windows Nein has given us about a man-year of unplanned maintenance so far, so you see how happy I'm about it)