Apparently with Alien 3 they fell out with the director and released a completely different movie, there's a fan edit and it's completely different. Shame there's just no way to get your hands on it.
The mess in Alien 3 is all on Weaver, she was constantly asking for re-shoots and re-writes...not trusting Fincher as he was essentially a nobody back then. He rarely talks about it in interviews, still a very sore point for him.
Gonna be watching the directors cut of A3 over the next few days after just watching Alien/Aliens at the weekend, will be able to tell you how much it matches the Assembley Cut and Hybrid Cut afterwards.