Allowing to upgrade a not updated installation

Wed May 19 21:47:05 UTC 2010

I began to take a look at bugs on
https://wiki.ubuntu.com/UbuntuBugDay/20100520 .

Looking at https://bugs.launchpad.net/ubuntu/+source/update-manager/+bug/576923
and https://bugs.launchpad.net/ubuntu/+source/update-manager/+bug/576920
one can see that update-manager version is well under 0.126.9.

I am asking myself why does update-manager allows an upgrade without a
prior update?
Or at least does it warns the user before accepting?

How well update-manager is expected to be able to handle an upgrade
withour prior update?