The feature is about adjusting the volume of a group of speakers together. That doesn't sound like the kind of thing that you'd need to copy Sonos' source code to implement. Maybe that inside look lead Google to decide to enter the market, but I really doubt the person who wrote the speaker-group volume functionality had ever seen anything from Sonos. If they had they'd be facing copyright infringement lawsuits too.

Ultimately software patents don't really care how something is implemented, just that it has the functionality defined in the patent. So for this ruling it doesn't really matter if Google copied Sonos or not.