I have only distributed to YouTube Content ID, why is my music on YouTube Music too?

YouTube Music and YouTube Content ID share the same feed. Due to the channel requirements, an asset in YouTube Content ID must be linked to an art track on YouTube Music. This means that when you distribute a release to YouTube Content ID, it will also be automatically to YouTube Music. If you don't want your release on YouTube Music, it is necessary to take it down from YouTube Content ID as well. This is why if you request a takedown from YouTube Music, it will also be removed automatically from YouTube Content ID.

If you'd like to keep your music on YouTube Content ID but you'd rather don't have a topic channel, you can merge both your topic channel and artist channel by creating an Official Artist Channel. You can read about how to do it here.