Aye. That's exactly what he said. Whether we can take that as canon or not, I dunno. Alpha one wasn't a philosopher or a cultural expert on the shivans, he was just an out-of-work fighter pilot.
As for the rest, we don't know. The Shivans don't seem to occupy any systems, but they do have a never ending train of supplies and warships and new shivans.
Furthermore, the shivans do seem to be taking a 'no more then is actually neccessary' approach. They could easily have sent in those Satanai immediately after discovery of the knossos if not during the great war, but they didn't. Heck, go play through Their finest hour again. Despite that the shivans have hundreds of juggernaughts in system, they don't send one out to trash the collusus until after you've destroyed 3 cruisers and a Ravana class destroyer.
All things considered, it's possible even the giant juggernaut fleet was nothing more then a shivan science expedition to study the effects of supernovas or local subspace or whatnot, and their real military is still at home.
At any rate, the only sound advice to be given on shivan technology and size is, "Never say 'we'll show them what firepower' is all about'. Cause you won't."