Interesting idea that makes sense, but it is just conjecture. Would need proof.
I think it was a rock concert ampitheatre. :-)
I remember years ago being very interested in Stonehenge and I was in grad school. There was an older soil study done with core samples within Stonehenge in several places and a layer of ash was present. That supports this theory (it’s not new) that there was a heavy structure on top that may have burned, but Stonehenge is likely so old that any wood present would have disappeared on top of the ground.
With that said, the mysteries of man pale in comparison to the mysteries of God! It is an interesting place to visit and pictures don’t do it the justice of standing there and wondering.