You can't just install security updates in Windows 7 any more. The only option via Windows Update itself is the monthly roll-up that includes everything. You have to jump through hoops or have a centrally administered system where the admin is jumping through hoops to do anything more selective, such as installing only the security updates.
It's a question of trust. That user no longer trusts WU to not silently install Windows 10. The window might have closed, but who says it won't open again suddenly, or a WU bug won't make it think it's still inside the window?
Silently installing Win10 from Win7 at this point after the window has long closed would be a massive controversy and utterly unprecedented in the industry. Updates introducing bugs is always a possibility on any platform Windows or otherwise, so the suggestion is just to stop installing security updates? Please.
Silently installing Win10 from Win7 at this point after the window has long closed would be a massive controversy and utterly unprecedented in the industry.
So was pushing the original Windows 10 update from Windows 7. That didn't stop them.