Actually, what the article is talking about is supposing an application or OS itself, needs to update itself, Vista
can replace files even when in use, but choses not to.
Normally, the Installer calls upon the
Restart Manager, to see if it can clear that part of the system so that it can be updated. If it can do that, it does so, and this happens without a reboot. If it choses not to, then this article explains why it choses not to!