Apple TV 4k audio

When I go into audio settings/audio output and select my receiver (onkyo tx-nr656), it will switch my input to airplay and play sounds, which sound a lot better by the way vs selection apple tv, but obviously there is no pic. If I change the input back to Apple TV, the pic is there but no sound. I figured this option was there for those of us who have receivers and want the better sound. Is this not the case? I can’t figure out a way to make this work. Latest update on apple tv and receiver. Apple TV hooked to receiver. Any help is appreciated before I give support a call in the morning. I couldn’t find any questions relating to this specifically.