The single value classes enable Page-list and Page-group property types to act similar to value lists/groups with less limitations. Given this use can and the scan of similar "-Text" classes being empty I don't believe the type of class you are referencing exists. What is your targeted use case?
Thanks for this: the use-case is (I said it was a bit esoteric!) was use a Java Step to examine Java System Properties; and just build up a PRPC Page of that data - in a 'key/value' pair way that reflects the original properties.
I was just trying to avoid having to create a specific Property of type PageList (of type 'SingleValue-Text') ; since would only be a temporary page; so that I could just create a simple, single-rule Activity.