I visited this place today... I would agree that the topography of the "embankment" is indeed mostly natural and there fore unlikely to have been a henge similar to Mayburgh (NB No expert)
If you look again at the OS map, the land around the Hall is a bit higher than that of the other sites.
It was impossible to get a photograph representing the layout...
I took some pictures of the inof board which I will persuse and post anything interesting shortly

I think it's just a massive coincidence that the position of the sites are in a threesome.

.o0O0o.