Play audio from Audiobooks and Apple Music at the same time on my iPhone or iPad.

I can do this on my MacBook Air without doing anything, just play the audiobook and choose an album from Apple Music. Both play seamlessly to my AirPods Pro's and the individual volume for both can be controlled on each app. The reason I do this is to add ambience when I am listening to an Audiobook, for me it creates an atmosphere and enables you to get into a "flow" quicker. For eg The Martian Audiobook and Space Ambience - Moving Gradients, in loop, is amazing in spatial awareness.

Now why am I unable to do this on my iPhone or iPad? It must be possible as I can use a work-around with Endel and Dark Noise and play the Audiobook and the aforementioned ambience apps at the same time which works great. However it would be awesome if it could be done with Apple Music same as on my MacBook Air.

Come on Apple, make it happen please.