Rune of Hagarrad path mechanics

I was playing around with an Infiltrator and found that the RoH pathing when the rune is set into a hole (eg: where the Aether Crystals sit around in holes around Burial Hill near Devil’s Crossing) means that the ‘arms’ have a good cance of being blocked form going further. Can anyone explain this to me? I’ just curious about the mechanics is all.

You can see this same effect with boss attacks sometimes if you fight on a slope. Bonehunter and Viloth in particular I notice it with. In short, if the projectile intersects a ‘wall’ it stops, and the terrain in places counts as a wall depending on the elevation of the projectile’s source point.

I don’t know what the criteria are for wall vs. slope because on some slopes the projectiles seem to travel along the slope and on others they are intercepted and stop.