Yes, it comes back to liminality (sorry!) and land boundaries, but it could be reversed for interpretative purposes. With a standard long barrow it's accepted that these were often constructed at impressive settings alongside a territorial boundary. (Toothells is the ideal example). What if, for instance, stone ircles were built to straddle an existing territorial boundary ? This would usefully explain why so many were then superceded by overlying boundary walls. (Another explanation is that the Boundary Commissioners were puritans who despised native art). Curiously there is an upland circle near my basecamp that is bisected by a wall - the boulders remain on one side of this wall, on one side, but are entirely missing on the other. This is at 'Longpot Head'.