I've had a couple of theories too. My friend said, maybe you get more units on the field at the same time. But apparently not. So then, playing Geonosis, the Sepratists boosted from 23 to 53. I was a little confused, but in the end we won. Secondary reinforcments is tough to understand but this is it. When you have at least 2 CP's or more, and you are losing by maybe 20-30 tickets, your count will go 20 or 10 above your enemies. It's really odd to explain, but it gives a hint in the manual by saying that if you have 2 command posts, reinforcments can still join.
'Helping all in need of SW advice.'