If for instance someone recorded all their own training data, designed their own NN, trained it, and prompted it would that be enough or not?
No, not for me. If the person involved doesn't understand how or why the sounds created are created/assembled, then they are not the artist IMO. The artist is the one with the vision, with a clear idea of how it should sound. If they are not in control of that, they are not the artist, IMO.