This is probably correct.
Here is a good article from a jazz fan who managed to finger Spotify for just publishing a whole library of ghost jazz musicians and adding them to their playlist. Not only that, but he ran into the exact same song several times, but published under different names and written by different "artists". However, it's not clear if some or all of these are AI, or simply some piano slave paid to make a song and relinquish all control over it to allow it to be republished under a bunch of different AI generated names.
My personal opinion is that it's a mix of both, and Spotify are trying to figure out just how much fully AI content they can slip in before people manage to notice.
It's as good a genre as any to try it out with since jazz is often just used as background music anyway, with nobody actually checking to remember a song title they really liked.