From what I've gathered is they do this if they fail to path essentially. The AI makes a path but if it can't it just skips to the end and teleports to its end goal. Bungie really should change how it works especially since the reason it became obvious was only thanks to the fact unstoppable ogre's (Well ogre's in general really but mostly unstoppable ones) would teleport straight to the ADU and if you found where they spawned they'd seem to just stand there and only turn to attack you un-moving for a few seconds before teleporting straight to the ADU. It felt like a guaranteed loss whenever hive showed up simply because of this happening pretty much 100% of the time causing the ADU to break quickly.