I assume in most cases they're literally the same files. Youtube runs "topic" channels for music that distributors have sent it.
https://www.youtube.com/channel/UCYOa-hi751OKY2zGJJv6V2A
https://www.youtube.com/watch?v=MSSxnv1_J2g (same thing, but on an official channel instead)
You can load any youtube music song on youtube by just removing the "music" subdomain.