Also some things have funny effects, in my yet unpublished Anno Domini mod which starts from year 300 AD so Romes are still big it gives Western Rome tens of 2-5 unit legions, instead Eastern Rome has only a couple of stacks but the all have over 20 units. And this a real headache at times.
I think it could have something to do with Regions so every region has at least one unit at the start because that kinda makes sense with my Western Rome having all of those small regions in france and germany, in the east there is only greece, asia, syria and aegyptus or something.