It is important to remember that the guy talked with an Apple representative and she couldn’t explain this to the guy. Or maybe the guy didn’t get it. Maybe the blog post would have been different if she would told him “there was a dialog asking you if you wanted to delete your local files and you tell it to do it”. For some reason the guy finished his communication with the Apple representative with the idea that Apple Music uploads your library and deletes your local files. Then only serves mp3 versions of your backed-up files.
So, he experienced this situation, talked with an Apple representative and end up with the idea that Apple Music was having a dangerous behavior. He made a mistake or the Apple representative made a mistake. Hopefully this will help to improve the situation and less people will be losing their music collection. Also, more people will be more aware of the dangers of subscription-model services.