As far as I can find the only plugin that allows for the assignment of page categories is Misiek's (http://wordpress.org/extend/plugins/misiek-page-category/) which rather than using the post category types makes its own list. Please make RS aware of these categories instead of defaulting to the post categories list.

It would be far easier to exclude (or include) folks from reading the 'secret' group vs having to monkey with sub-page hiearchy work arounds.