As the RPL has been touted as a licence that fundamentally replaces a GFPT, I think it's pretty clear they meant for flights to happen in the local training area of the aerodrome where the aircraft is based, and for anything further afield to require a nav endo.
As it's a licence, though, you don't need a school, instructor or a training area to fly in once you've got it, hence the 25 nm thing to replace the concept of 'don't fly far from your home base until you know how to navigate'.