No, these members do not have access to the Allowed Member List (Hidden) forums (Unless they are added by you in the two boxes where the rest of the member are listed). That option is there so that if you do add a forum which is open to public you can either choose: Do Not Set Read-only Deny
I typed this from memory. I would have gone to my forums but (hehe just my luck!) my forums are down...just after I check my messages. I am sure this is all correct and anyone here who sees something not, is sure to let you know in this topic.