What happens when averaging skylines?

If I have one horizon at point A and 2 horizons at point B, would that give a different result than having only one horizon at each point? Averaging as implemented is a simple function. If you take two Skylines at one location, they would have twice the weight of a single Skyline in the average. It is questionable sometimes what is the physical meaning of averaging the solar access numbers. It is often used in US rebate programs, since the average is more accurate than a single value. However, it may not be the best for determining solar production.