A Foeldrygarn puzzle

This is a photo of one of the microgabbro outcrops near the summit of Foeldrygarn.  The outcrop is a small one, surrounded by grassy banks.  It's a degraded small tor, but here the focus of interest is the semi-circular arrangement of stones set in the turf.  This is quite unlike anything I have seen elsewhere in Preseli.  There are plenty of semi-circular stone banks set against small cliffs in the uplands of Preseli, but these are characteristically composed of curving lines of boulders or low ridges up to 2 m wide.  Some appear to have been low walls that maybe supported roof timbers -- with the upper ends of the timbers supported against the rock face.

Here on Foeldrygarn we see a "band" of large boulders or slabs, many of which seem to have been placed end to end...........

The site lies within the summit hillfort and not far from the triple Bronze Age burial mounds -- all made with locally quarried stones which were carried short distances uphill.  The stones were all small enough to carried by one man -- or sometimes two men working together.  Large boulders and slabs were rejected on the grounds that they were unmanageable -- and maybe this holds the clue to what was going on.  Maybe the "band" of large stones was made entirely of rejected stones, pushed aside while the smaller stones and finer debris fragments were carried away for the construction of bural mounds and later for the fortified mounds that are prominent features of the site?

Has anybody seen anything like this elsewhere?  Any other theories about what was going on here?