This is apparently still a thing. I’ve now had two hard freezes in this weekend’s HoD, once after persistent nightmare attacked and should have been moved to my (empty) hand, once after I killed my own persistent nightmare with my noxious gearhulk’s etb effect.
I did manage to kill both sides of the card multiple times with no issues in other games with the same deck, so this doesn’t seem to be an all-the-time issue but it has definitely managed to completely devastate my otherwise perfect score this weekend and lived up to its name quite well