Nice critique. I never really used Buzz, because my first instinct was to turn it off, but what little experience I have with it seems to match up.
I've never worked at Google, but I know someone who interned for the UX team, who complained that UX wasn't as involved with design as they could be. I'm guessing that the usability of non-core Google projects depends a lot on whether the engineers who start them seek input from their UX people. If you're doing a 20% project and want other people to work on it with you, you've got to find and convince those people yourself. So at least initially, the involvement of UX people outside of core Google projects depends on whether their involvement is sought.
Buzz in particular appeared to have been launched with little forethought, so there's a good chance it didn't get much of a UX pass, either.