This is from @Stevesky, apropos AirPlay and Apple Music:
In a follow up in the Beta forum @Liam mentioned that the reason the “now playing” screen doesn’t show bit rate / bit depth info is because it’s always the same format delivered over AirPlay (ie it’s expected behaviour, not a bug).
Doesn’t seem to be a way to set or select this, as @Simon-in-Suffolk observed. The spec allows more, but it hasn’t been implemented.