If (as as it is) Apple is still controlling apps via notarizarion/digitally signing apps of and recognizing developers, and if the app is developed for something that would land Apple in legal trouble (e.g. it makes it easy to freely and illegally download music and Apple also has legal contracts with record labels as they have Apple Music, and not only legal but it also affects Apple's own music revenue too) as the app has passed explicit notarization of Apple (in other words: Apple "knowlingly" allowed them and greenlighted them by notarizing the app), wouldn't it cause legal trouble for Apple?
For that, it's the logical behavior for a company like Apple to stop allowing the app.
Again, I'm not supporting it, but I can imagine where it's coming from and that makes sense from a business perspective as torrenting on mobile has almost no legal use cases. We all know you have not installed it to download your favorite Linux distro to your iPhone.