Funnily, your comment, “My own view is that the stones that are dressed/worked/smoother faced on the inside are possibly built for 'religous/ritual' or something other than day to day practical use...” leapt off the page because that is exactly what you see at the Anglo-Saxon church at Greensted, where the 9th century oak walls are undressed (round) on the outside but dressed to a flat, continuous wall surface on the inside.
You have to experience for yourself what a continuous, flat interior wall of ancient oak feels like but it’s not a million miles removed from what you’re suggesting above.
I think it makes sense that if you are going to build something that will be 'used' internally, then that is where you concentrate your efforts on. And the fact that you are going to that extra trouble on top of the sheer effort required initially to get the stones collected and erected in the first place, shows its importance to the people of its time. Being a carpenter/joiner (retired) I can appreciate the immense skill required to achieve that wall finish you speak of.