I think it's most probable, especially after hearing that interview, that SEGA contracted Michael Jackson to do the music for Sonic 3, he quickly lost interest and tasked Brad Buxer with managing it. Buxer then made the 41 cues with the 'MJ Team' credited in the game and that's basically it. I don't really think there's much mystery around it anymore, at least whether Michael actually contributed much to it. With the Jam vocal sample and the music similarity between Carnival Night and Jam, I imagine that's the work of Buxer. Buxer's not credited as a songwriter on Jam, but he is credited as working on the song. If I had to guess, Michael Jackson isn't credited because he didn't care about it. And from SEGA's point of view, they were probably happy to have his team credited and not Michael himself after the scandals. It wouldn't have felt bad for them to do so anyway, considering Michael had basically nothing to do with the game.