Only shows nodes with Published status

As a newbie to Drupal and Nodes in Block, I'll seek forgiveness first, in case I need it :)
I've assigned this meantime to Documentation - please correct if necessary.
This is Drupal 7.8, Nodes in Block 7.x-1.0. Sorry, I haven't tried a -dev version.

As far as I can see, for any node to be visible in any NIB block, the node must have its "published" flag set. Even as administrator, I cannot see unpublished nodes in the NIB block, but setting the Published flag on the node makes it visible in the expected NIB block. This is a problem in my scenario below.

I'm using Nodes in Block (NIB) to control which articles (nodes) go into "In This Edition" (a NIB block) in each edition (a basic page) of a local newsletter. That seems to work as I wanted - thanks !
I'd like new articles to be assigned to an edition named "next edition" (visible only to certain user roles), so they can be reviewed before publishing them in a future edition.
Because of the behaviour of NIB, I must mark these new articles as Published before they have been reviewed. I can make the "next edition" page harder to find, but the content is still potentially visible to all users.

Is this intended behaviour ? Where would I look for this information ?
Or should normal permissions control visibility (as I assumed) ?
Is there a workaround, or a different/better way to do this, or a better place to ask ?