I can confirm that there is some bug that causes a second claw to randomly spawn when we left eyes up from previous phase. I can't say if it was a fail or eye since I'm a healer and don't really pay attention to that, but our usual strat is to leave 2 eyes up on 3rd black, so I would assume its that.
I think its more just a bug rather than blizzards attempt stop players from circumventing mechanics. I also believe the way the debuffs interact do not work as intended when leaving eyes up as the damage during the fourth black phase always seems to be less than others, though it just may be a result of stronger healing power from bloodlust + everyone remaining stacked for the duration.