By default, Google holds the copyright to open-source projects released by Googlers. There's a review process for transferring copyright to the individual, but you don't have to go through it just to release something.
Yes. The fact that we own some code doesn't mean it's officially supported. It just means we try to maintain accurate info.
I actually want to simply eliminate the copyright notices since they are legally pointless, but any time we've done it at scale it just generates lots of questions about ownership, even with clear info in README files, etc.
edit: See previous comments from DannyBee and cdibona here: https://news.ycombinator.com/item?id=4051325