It will be interesting to see how/where the line is drawn on "in substantial part", considering that Logic Pro lets you click a button and adjust some sliders to add an (awful, imo) drum/instrument played by AI to your track.
This is IMHO an impossible line to draw. If an established artist uses a GenAI music tool it would be accepted. If somebody unpublished does the same it wouldn’t. Assuming they can even tell the difference, which they can’t.
But that's absolutely not generative AI (which bandcamp explicitly stated the policy is for) and it's not even classifiable as traditional AI. The session tracks are just some base patterns selected by sliders attached to options adjust stuff like "play these notes in an inverted chord".