Well that depends on the menu structure. If the user visits the parent page that is not included in the menu and the parent page has a child page menu/sitemap on it then the user should see the child pages assuming the same as above that the user is in an allowed view role and either in an edit role or draft edit role.

However, menus are hierachal, the child page menu starts binding below the parent therefore it can show the child pages even when the parent is not included in the menu, similar with PageMenu if it is configure to bind nodes starting below the parent it can show the child pages. But in any menu where the parent level is also included, the the child pages cannot be shown if the parent is not shown since the children are below the parent in the hierarchy they hang off the parent page and they cannot be shown if the parent is not there. So in a case like the site map its just a single menu with the entire site hierarchy, any page that is not included in that menu also removes the sub hiearchy below that page. ie there is no way to databind the hierarchy below the parent if the parent node is excluded from the tree structure that is the hierarchy.

I agree.  Thanks for the bug fix.  Will pull and test tomorrow morning.