Uber Arbiter Level

I've killed the Uber version of the Arbiter of Ash (the one from the Calamity fragments) about 10 times this league. And he has always been lv 82 with 5 mil hp and dropped ilvl 84 items. Frankly, I didn't see any difference between the Uber and non-Uber versions. They were both lv 82 and seemingly the same difficulty.



But the one I've done just now had a whole lot more hp (20 mil) and all his drops were ilvl 86! Which means he was lv 84!



It would make sense for the Uber version to be higher level and tougher than the regular one. But then why isn't it always lv 84??

Is there a bug that makes Uber Arbiter spawn as lv 82 most of the time? Or is there some weird design that he only spawn as lv 84 rarely?