Anyhow my take on it is this:
The Death Star was being constructed from the end of AOTC - when Dooku got hold of the plans and gave them to Sidious.
It was a secret build - hence the new style uniforms. This was like 'the Death Star group' if you like - along with the new type Star Destroyers and Tie Fighters. This was all part of the Emperors long-term plan to begin his Empire. He obviously knew what going to happen so put this whole operation into plan a couple of years before the events of Sith.
But, who really gives a shit. It's just a film!
