Looking at the story, it sounds like a bug that wasn't considered needing allocating to a top tier support fix, but making it public required them saving face.
Nothing new there for any company.
They knew about it, looked at it as whether it was important and then evaluated it wasn't worth the fix across the board, due to IPv6 not being the mainstream communication door, IPv4 is, and quite often IPv6 is uninstalled on systems due to being a a source of bugs on computers.
Thanks for the news though ant, it is always good to hear bugs are fixed. --
The only thing necessary for the triumph of evil is for good men to do nothing - Edmund Burke