i opened the music app on my watch, clicked the airplay icon, and i see all of my home devices (homepod, apple tvs) listed. even my mac mini is listed.
You can test this out quite easily: play any audio from your mac (YouTube, Apple Music, whatever) and then try to pause it on your watch. This is not possible.
Spotify Connect allows you to do this easily on the other hand.
Still, this does not seem to be what OOP wants.