Not much of a justification in that link. They got some classical experts to make curated playlists. Sure. Put them in Apple Music along with the "experts" who pick everything else. Or is this an admission that the curated playlists are very generic and pretty crap?
If it takes a special search to find classical stuff that isn't in the app, why can't I get those kind of search features for jazz? I may well want to search for a jazz standard by composer instead of artists, etc. So Primephonic is supposedly "optimized for classical, premium-quality audio". Shouldn't all Apple music be optimised for premium quality audio and being classical makes no difference to other dynamic forms of music (and various prog rock stuff is far more dynamic than a string quartet and more akin to an orchestra). So it makes no sense to put it in a separate app when I want to listen to all styles of music and not have to have 2 apps. Just make the Music app more customisable! Sure if I look in playlists there's not much classical, it's pretty limited and you get a lot of pop rubbish, but fix it so I can customise what playlists and styles I want up front. If not, lovers of classical may get a better experience but everyone who loves jazz, or world music, or hard rock/metal, etc will still be stuck with the usual limited layout and playlists, when it could have been a great opportunity to make it really work better for everyone to get a better layout and music discovery.