"if such a sophisticated and accomplished piece of landscape art should be the ONLY one of its kind".
Stonehenge, Silbury, Avebury, Callanish, Arbor Low ........and yes Abbeyquarter North ..........the list is endless - all sophisticated & accomplished pieces of landscape art , all one of a kind

The point I am trying to make is that we have only one example of a prehistoric hill figure - Uffington - it IS the ONLY one of its kind that we know about. Are you saying that " Stonehenge, Silbury, Avebury, Callanish, Arbor Low ........and yes Abbeyquarter North " are hill figures??

I fail to see what you are getting at.