This is, I stress, entirely speculative on my part - there is no confirmation that the geophys results do in fact record buried stones, nor is there any dating evidence associated with these buried somethings as yet.
However.... consider this.
Perhaps the original monument at Stonehenge was (as Mike Parker Pearson suggests) some 56 bluestones arranged around the inner perimeter of the henge bank, dating to around 3000BC.
Perhaps *at the same time* there was a similar (sub)circular stone monument at Durrington, although built of sarsen.
Could it be that in 2500BC a decision was taken to combine the two monuments into one at Stonehenge, utilising the materials (bluestones and sarsens) from each site?
Is the neolithic village at Durrington Walls (dating to around 2500BC) related to the dismantling of a subset of the existing sarsen monument there (ie some 75 or so stones) in order for them to be transported to Stonehenge just over the hill?
Are those that remain at Durrington (if they are indeed buried stones) just the ones that the builders rejected?
An auguring survey at Durrington is desperately needed to discover if these are indeed buried stones and if there is any associated dateable organic material.
Durrington Walls Geophys