AirPlay is different from the desired functionality. It basically uses your mac as a remote speaker, instead of actually opening the music app on the computer and playing music there.
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.
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.