At times we've issued "the same proc with a new name" as a way of allowing us to get feedback on extensions to that procedure, without completely putting everyones production workload at risk. In the past we've seen TREPORT - new features in proc report; TFREQ - new statistics in proc freq, and SORTT - the threaded implementation... Sometimes we can prototype new features simply with new options in the existing PROC. It's usually a judgement call related to how invasive the new feature is to the structure of the production code.
We want power users to kick the tyres (for my UK friends) on some new features or implementation before they become permanent... So they remain undocumented (mostly) because the features are "transient" in the sense that they migrate into the "official" versions of the procedures, or they were not such good ideas to start with. And they remain implemented (mostly) so as not to overly in-convenience any early adopters who have been so bold as to use them in production jobs... Hope that helps y'all understand our motivation (at least a little bit)
I've not found a use for this information yet, but I thought I'd share it with you nonetheless!