Its always good to see this again though it feels as though it has been repeated more than once. My ears pricked up this time at the mention of Cairn Holy which I visited earlier in the year almost by accident (en route to Stranraer ferry). The site blew me away, I would like to always remember the peaceful walk through woodland up to Cairn Holy, not knowing what to expect.

Anyway, Neil Oliver made what seemed like a fleeting visit meeting Professor Julian Thomas there and linking the site to the long mound digs which took place at Dorstone Hill, Herefordshire, in 2013.
https://dorstonedigs.wordpress.com/
So he seemed to be saying Cairn Holy may have started out as a timber hall (made sense, on a hill with nearby spring) which was later burned and turned into a monument to 'founding generations'.
Food for thought ... and I confess I missed it the first time round.