Good question. I assumed it was only when using the streaming apps (which I already assumed have some sort of unique signature) but I see they don't explicitly

Good question. I assumed it was only when using the streaming apps (which I already assumed have some sort of unique signature) but I see they don't explicitly say that it is app only. They mostly just call them streaming services. Only once do they refer to apps when they say: App after app, we’re setting streaming music free.