It's supposed to Just Work on clean and rescue systems. Otherwise, it's a regression with respect to v4. The fact that it doesn't work is evidence that someone has been doing something wrong. The user at the receiving end of this clusterfuck is not that someone.
No, I did not bother because I don’t use IPv6 and I don’t plan to use it anytime soon.
Reporting an issue usually involves some effort, and the support may decide to follow up even if I say that I don’t need a fix. It’s better if someone who cares about IPv6 reports it.