When will the help center contain information relevant to this site specifically, or does it already and I just can't find it?
Some help center information can be edited by moderators. Since we do not currently have moderators (and won't until we're public), it can only be edited by staff I believe.
It would be good to bring this up again once we have moderators or bring up another Meta post asking what should go in the help center.
That is a part of our job on meta to discuss the exact wordings we want to have in the help center and which questions we want on the tour page et cetera.
If we in the private beta have more precisely defined the scope we can fill the help center and the tour page with exactly that information.