TWINBIRD,
You are quite right, it is confusing. Both QRH and RFM say that the starter gens are on DC essential, and they are appear to be in the DC essential area on the overhead c/b panel. So why do all the training manual circuit diagrams show them off the main buses?
I have been trying for a couple of days to bump into one of the groundschool experts and ask them over a coffee. If I manage to pin them down and get an answer, I will post it on here.