Not sure about those. The Stanton Drew one was probably part of a chambered tomb of some sort.
More like the little arrangements on Exmoor or Bodmin Moor perhaps?
There are currently only 14 on TMA (neither of the coves, nor the three stone setting at Llanfechell on Anglesey).
https://www.themodernantiquarian.com/browse/site_types/stone_settings.html
King Arthur's Hall is nothing like the others either.