Serenity Caldwell, writing for iMore, looks at what may have happened in regard to the blog post going around saying that Apple Music deleted a bunch of files off someone’s hard drive.
Whatever the case, Apple Music was never designed to delete Pinkstone’s source library, and it won’t delete yours. That’s simply not how the service works on your primary Mac. But if you’re not aware of how iCloud Music Library stores copies of tracks, you may delete your local copies to save space, thinking you can get them back — and get screwed as a result.
My guess is that there was a misunderstanding in how the system works, because the system is pretty stupidly confusing at times, and there is always the chance it was a bug. But there’s absolutely no way that deleting your music, without you expressly saying to do it, is “working as intended” as apparently the original author was told by tech support.
What I consider to be the killer feature of Apple Music, the combination of my local library with their streaming library, is also the feature that adds the most complexity to the service. While it does work, and I do use it, it’s far from perfect and definitely confusing. That’s on Apple to fix if they want you to trust your music library to their product. If they don’t have that trust then people will continue to use two apps: one for music they own and then Spotify for everything else.