On macOS the feature is baked into the OS's APIs, the app developer just opts into using them. If they don't, quitting with unsaved work will prompt the user modally, and block the restart to the point where the OS will timeout the reboot process and give up. The only way to purposefully lose unsaved work in almsot every app I've ever used on macOS is to yank the power cable or hold the power button down.

Window locations and app state are written to plist files, again, using OS libraries and APIs for app resume. I can reboot my Mac and not even realize it happened sometimes it all comes back the way it was.

The blocking happens on Windows as well, except that the timeout logic is the reverse: it force-quits the applications then, because presumably the potential security update is more important.