No worries, it is confusing. The owners of the announcement mailing list at Google receive the message, even if it bounces for you. If we then reply, we're allowed to post to everyone as we're owners, which has caused some confusion for you all except for the original sender, as you didn't have the context of the seemingly bounced email. We now work with an automated labeling system in Gmail so hopefully this human error of us replying by accident to bounced emails doesn't happen again. Apologies for the inconvenience.
We do reply-all on this discussion mailing list. Be sure to make use of the "mute" feature in Gmail if you're no longer interested in a thread.