Administrators cannot restrict View/Edit of a page to a group that the administrator does not belong

As administrators, sometimes we create pages that should be viewable by only certain user groups. However, the restrict View/Edit in V2.1.1 allows only restriction to "myself" or the groups that the administrator belong to. The problem is, it does not make sense to disallow administrators permission to assign a page to some group the administrators do not explicitly belong to. When we have over 20 user groups and counting, it is not practical to add administrators to each group to make this work.