Comment 2 for bug 772164

If 10.10's installation medium was only 2.1GB, for both the desktop and netbook edition, then 4.4GB isn't that much difference once you combine them. It would only be ~0.2GB difference to combine 10.10 in the same way.

As far as your problem, I have no clue as to why it would be wanting to install all 4.4GB of media if there are 2 separate versions on the disk.