Actually storage in the sd card is permitted by Apple Music, it is an option to choose.«Practically, Android allows you to install almost every app on the adopted storage. But it also requires the consent of the app’s developer. He has the freedom to enable or disable support for adopted storage in the app by adding relevant attributes in the code.»
Maybe its time to ask your question to apple...
https://fossbytes.com/android-sd-card-internal-storage-adoptable-storage/
I have installed the application in the internal memory.
Maybe I can try to install the app on the sad card, another interesting test.