The question I have is, why would they beta an old build? I'm a software dev (not in the games industry), and typically when we have a beta out it's ahead of the release candidate branch, not behind it. It really doesn't make any sense to me to have customers testing software behind the release candidate. When you have a beta you are releasing the most stable build you have in an attempt to shake out things you missed. If you have a release build that's going to go public in a few weeks, what possible incentive is there to not beta that build?
This is not to say that there isn't branch of code at Ubisoft which has additional features or fixes. We have a development branch where we put "dangerous" code. Meaning, code that touches a lot of the software, core changes, or any major new features. I can see Ubisoft having fixed a lot of issues we are complaining about in a build that's still early in the QA cycle, or not at all yet in the QA cycle.
No offense, but the only thing I can think of is people's blind optimism. So tell me, logically, why would they beta a build that's months old?
Edit: To clarify I said months old. Obviously there's a few weeks between beta and release so the release is probably going to have a few weeks worth of work done to it.