Not sure about the visual aspects of a builder not displaying something different - most builders like their work to be a little different, gives it a more personal touch. I can appreciate the developer maybe not wanting to show something that could be controversial and might cost him money, with rock art maybe being seen as black magic, and of course there is the chance that the markings would not have been noticed and the stone just slapped into place.

Just think, all those abandoned cottages with art hidden in their sunken stones...