The trouble reported earlier with Apple Music seems to have attracted high level attention. James Pinkstone had reported that Apple Music deleted countless unique tracks he had stored in iTunes, and that an Apple service rep assured him this was correct behavior.
As he describes in a later blog post, Apple contacted him promptly. They assured him that file deletion is not an intended feature of Apple Music, and they sent engineers to try to figure it out.
This doesn’t change my own conclusion: the only way to ensure ownership of electronic media is to remove copy protection. This requires a bit of geeking around on a desktop. If your ebooks and music reside exclusively in proprietary apps, like Kindle or the Apple products, then the vendor can delete them at will. It happened on the Kindle.