I heard Joseph Campbell, of the Power of Myth fame, talks about Nepalese temple architecture in one of the Power of Myth episodes. I am not sure if he addresses this specific aspect of architecture but my curuoisity has peaked and I may buy or rent the series to see what he has to say. I did catch some of the episodes on PBS but must have missed out on the one about Nepal. By the way, the story I heard was from a guy in Patan who had family in the wooden sculpture business. It is most likely a grandmothers tale passed on down generations and may not have a sound factual or scientific basis.