So is this "resolved" in the sense that the changed behavior is now understood?
Yes it is resolved in the sense that the change is understood.
If it's understood, is it believed to be a good change that happens to break this person's apps
Depends on your point of view. I think the 2 previous posts explain this in depth.
or a bad changed that has caused a real bug?
I don't think anyone would call it a real bug. Think about it like upgrading your car. You may be happy that you can transport more but you can be sad you can't cross the smallest bridges anymore.