This sounds unusually stupid, even for Goggle - because they could've just poached a few engineers and it would be less risky than public, high-profile corporate espionage.
It's a core part of Sonos' complaint, I am sure you could find it in the legal filings, but this article about a preliminary injunction against Google in Germany about the same issue starts with that detail in particular: https://chromeunboxed.com/google-sonos-lawsuit-2021
This sounds unusually stupid, even for Goggle - because they could've just poached a few engineers and it would be less risky than public, high-profile corporate espionage.