Artillery Ballista doesn't target Xyclucian's stone pillars

Artillery Ballista doesn't target the stone pillars in Xyclucian's fight.
I tried placing them further away to avoid the "won't fire if the target is too close" limitation (if it's even a thing). I tried minion command key (not sure if it works with totems, but just in case), the pillar highlights in green but no change in behavior. My tamed beast had no problems attacking them.