I was wondering about this too. In her latest newsletter, she described the facing side of a house as the yang, public, bright side of the house. The sitting is always opposite the facing and is yin, private, dark. The facing side is the side one would take a picture of. Because we are living, we are yang, and we need to be supported by the yin. That is why I've chosen to subscribe to the notion that the sitting direction is the direction that determines how the qi is distributed in a house for the living.
Consider a woman's dress. There is only one correct orientation for the dress to be worn. However, the zipper may be on any side of the dress: the front, back or side. It is the same way with a house. The orientation of a house is based on its sitting direction. The door is merely an entry into one of the nine energy quadrants. It is also where the qi is refreshed. This is just what makes sense to me.
Regards,
Mark