They acquired Primephonic [0], an app and streaming service geared exclusively towards Classical music, a couple years ago. This month, they are launching Apple Music Classical [1], which is basically a separate app and experience from Apple Music that is geared toward listening to classical music, likely built from Primephonic. Classical is included with an Apple Music subscription.
As you note, classical music has a distinctly different metadata structure than popular music, and the typical “Artist - Title - Album” structure in most streaming apps completely fails basic UX for classical music.
[0] - https://www.apple.com/newsroom/2021/08/apple-acquires-classi...
[1] - https://apps.apple.com/us/app/apple-music-classical/id159843...