Calm down, people...
A few more clarifications:
1) This feature is not enabled by default. It only gets triggered if a frontend tool makes use of it, and will not be activated automatically. So, you will only see it when you use GNOME with GNOME-Software or any other tool which triggers the functionality. Also, if it triggers the offline update, you will have chosen to do that by clicking the "Reboot and Restart" button.
2) I tried to reproduce the behavior of getting offline-updates by only installing PackageKit in a clean Sid VM. Everything was behaving as expected, no offline-upgrade was triggered without a frontend tool requesting it. So, there is something really strange happening on your system to trigger this - more feedback would be welcome. It could be that GNOME-Software was installed, has triggered the upgrade once and the file triggering the upgrade has just not been removed, so the machine will endlessly try to upgrade. Although, this should actually never happen, and I would be very suprised if it does.
3) If you want to complain, complain at GNOME for making this the default behavior for updating software. The lower layers are really not to blame here for executing a request from other tools.