Different DVD packages for volume one?

I noticed that on my DVD package it simply says, Volume One. However I have seen some packages that say, Volume One: The Early Years. What gives?

I think they initially planned to simply label each set as its respective volume number, but after a bunch of sets had already been printed, Lucas decided to add subtitles to the sets. If that's the case, it would imply that, although a lot of work may have been put into the content of the sets, their presentation may have been rushed.