There was no agenda behind building the quartz wall, in fact the brief from the Board of Works and the Tourist Board was to create a shapely hemispherical mound of stones.
The problem was instead of a solid mound of stones, behind the kerbstones they found layers and layers of compressed turf. When the turf was freshly laid it had to have been much thicker, therefore the mound behind the kerbstones had to be a lot higher originally than at other passage tombs. The quartz was found on the ground at the very bottom of the piles of stone that had slid from above. There was no quartz found under kerbstones that had fallen over so it is unlikely to have been laid on the ground, it was on the face of the mound as at other passage tombs like Cairn T at Loughcrew.
O'Kelly built a section of the wall back up and had it pushed over and then inspected the result and it closely matched his impression for how the wall should have looked.
There's lots of examples of near vertical stone walling in Neolithic monuments, Barnenez, Petit Mont, Gavrinis, La Hogue Bie. Newgrange would not have been the first of its kind, apart from the facing being of quartz rather than granite blocks.
