I remember seeing this published when I worked at Sonos. In fact, I might have been the one who put it on the Slack channel.
It was a cool project at a time when a lot of people were saying it was insurmountable to make us AirPlay compatible.
Sorry you didn’t get the job. I hope you didn’t lose much sleep over it. I left in 2020. I wouldn’t say you’re missing much any more.