The 573 is a recent model, so it uses the RX-A set. The naming is a bit confusing, but usually nobody runs into it as an — A member replied: “Thanks for the quick response. I've tried this on zone 1 and zone 2 but nothing works at all. I have the Yamaha app on the ipad and this all works so I'm confident the amp is set up ok.”
The 573 is a recent model, so it uses the RX-A set. The naming is a bit confusing, but usually nobody runs into it as an issue because the auto-discovery chooses the correct command set for you.