Yeah, that is true.
I was thinking about another way to detect this. Depending on your set-up, I might have another way. I have a Sonos One in the living room, where my Beam and tv are also located. When I’m watching tv, I obviously don’t want to listen to music at the same time. Therefore, when the tv is on, the beam is playing and the one is not playing. When I’m listing to music, I always use both the One and the Beam.
You could make a flow that checks whether Beam is playing and One is not playing, if this is true, the tv must be on. When the tv is on, the source of the beam is changed to the tv, so you have another trigger. Perhaps catch this in boolean, so you can use it as a trigger. Unfortunaltly, we can’t use the condition Is playing as a trigger, so you’ll have to find a work-around for that.
Just throwing this out there, without testing or anything