Thinking about it, I don't see why Apple and the iOS store are a specific target. How is it different from Sony having monopoly on who makes PlayStation games for example?
Or from another perspective - what principle entitles anyone else to have app curation/approval/distribution rights on a platform that Apple created if Apple don't want them there? And to be clear - this isn't an argument for or against closed or open platforms. I might personally prefer the more open ones but I think that it makes more sense if the creator of the platform opens it up if they want to instead of this being mandated by law.