So Google has decided to compete with Airplay. Although I guess this is better, because I'm assuming it will work with any router, and not just special ones sold by Apple.
That is true, but I also believe there are some lower level "nice to haves" they enable on their routers to make sure Bonjour/mDNS works properly for airplay. If not intentionally, I do know that some routers (Actiontec / FiOS comes to mind) that have particular difficulty with providing reliable Airplay connections.
It's actually more like Sonos. Airplay streams from the device to the receiver. With this (and Sonos) a command is sent to the device which does the streaming on its own.
This is the best news yet coming from the auto manufacturers and Android Auto/Apple Carplay. I personally would never choose one of the two, but the option will make both ecosystems more successful.