Benn like it since iOS 13 from what I can see, but I just discovered it so maybe others haven’t realised.
Can say "play (songname or artist name/ ) with YouTube music"
Great for AirPods where can tap to bring up Siri and pick song with voice.
Can also do custom short cuts for play lists and songs as well, the custom one works on iOS 12 as well.
From when loaded YouTube music can go into settings, Siri Shortcuts and every song or list played since YouTube music started will be there. Just hit + symbol next to it to create shortcut and can alter what it has for speech to start that list/song.
When close YouTube music the list is deleted, so it’s just the ones since last time loaded will be on list for creating short cuts.
I was slow in discovering that one lol.