Isn't it the same as a physical store refusing to stock your album because of something objectionable to them on the cover?
Who are Apple to say I can’t put another artists photo on my album?
Sounds to me like it’s primed for some artist(s) to break as many rules as possible with a legitimate release to see how Apple actually respond.
Are you not able to purchase music and import to the Music app with whatever metadata you want?
I am not posing a rhetorical question, I do not have experience with the Music app outside of using the Apple Music subscription service so I would like to know if they do restrict these kinds of things.
It's also user-configurable whether the app will move your files into its folder and organization scheme or just leave them alone where you put them.