I don't think this would be the reason behind all such carvings and still think each one must be assessed on its own merits, but it <i>could</i> be one of the reasons why that spot was chosen.
I know the main reason why the area (with over 20 carved stones) was chosen as due east there is a very low pass between two very high mountains and on the equinox the sunrise on that gap would be stunning from there!