As far as I'm aware everything goes there except for posts in CB and Q&P. However that's only from my personal observation, not from any knowledge of the Ed's policies.
Every one goes in as soon as there's a new answer, some whizz through quite quickly - the only ones which might not show are really old ones, like this one Ab Editor, where we have to supplicate to the Ed to get it reinstated every month.
Hi Boxy - I was looking at the Home page rather than "latest posts" . I think Chris is right about which ones appear that and which don't, but I'll keep a look out now and see if that's the case.