Why separate GA and updates directories?

[Bruno Wolff III]

On Sun, Jul 12, 2009 at 08:46:15 +0100,
  Matthew Booth <mbooth at redhat.com> wrote:
> Does anybody know the reason that Fedora separates GA and updates on its  
> repositories? In case the question's not clear, I mean this:

Probably it's at least partially because it's less work to build the repo
only will updates and no having to recompose the GA stuff over and over.