True that iOS does update by itself for the most ridiculous reasons... None with the consent of the user. Not much of a reason to update my older iPhone 6 since I've got all iOS 11 has to offer for years, and a lot more useful features. Hard to believe I've seen the occasional stutter and lag on my iPhone X, it's supposed to run flawlessly... what a disaster of a release.
So many people that I know who didn’t update to 11. It’s still a surprising how they’re at 65%. It feels like less than 50. As soon as 11.3 comes out with throttling option to enable and disable I’ll tell my friends to update. But for now the software is not much worth it.
I'd hazard a guess and say that most of the updates to iOS 11 happened while the "owner" slept.
Seriously, If the user says "later" they don't mean "automatically install without any my knowledge", they mean "remind me later as to whether I want my iPhone updated"
So, the figures imply that 35% are either jailbroken, have the tvOS beta profile installed, or they're on a 32bit device.