As far as I am concerned I have not seen any (desktop) version of Ubuntu where this feature works properly:
My expectation would be that when afterwards rebooting into a newly installed system running
apt-get update apt-get upgrade
should not lead to any further package updates. The contrary is the case: even before I manage to open up a terminal window to type in the above commands, the “Software Updater” pops up to announce there are several updates available – not the kind of behaviour I would expect when checking the corresponding box earlier in the process.