Question about Rikti Mothership Raid Pylons

[srmalloy]

I don't know if anyone knows for certain, but I figured I'd throw it out: When you're attacking a Rikti shield pylon with ranged attacks -- or any other target that uses the same model -- some attacks are targeted to hit the pylon at the base, and others just under the rotating head, twenty feet or so up the pylon shaft, but it's consistent -- any given attack power will only target one or the other impact point, and powersets seem to be capable of having different impact points for different powers. Does anyone know why this difference exists, and what the distinction is that determines which powers hit where? There's no difference in the effect of hitting, only that the attacks visually hit the pylon at different points.