Burl wrote something on it in Prehistoric Avebury, comparing it to some of the Carnac Mounds in Brittany which are larger.... and, though this is not often talked about, the fact that there is no comparable large barrows at Stonehenge, showing two communities that were separate not only in distance but in 'religious interpretation' of the landscape.
It seems strange that there are three 'very large' barrow/mounds near to each other, Hatfield being the other one.

I quite like the idea of 'hill altars' that Hoare apparently mentioned, think we discussed it before years ago; in Silbury/ Marlborough case, Picked Hill would be the model.....