I read that with interest actually. I did like the idea that one of the slopes points to the north star. I reckon though if I'd put it up i'd have had it so you could have had your eye closer to the rock while you were looking up the slope.
I quite like the shorter idea that because it's pointing at the north star, it's about the night sky not the sun - the stars turning on the axis of the pole star, like a millstone turning, or the 'axis mundi' the axis of the world... anyway I'm just getting carried away.