His style is all over Sonic 3. He is definitely responsible for much of the soundtrack on that game. I'd imagine it is a case of Sega wanting to distance themselves from him given the slippery slope he was going down. In the first video below, someone has the Sonic 3 tracks in a different format (don't know where they got them) and he is credited on the tracks meta data (meaning Sega scrubbed his name from most places but forgot the meta data) One of the producers he was known to work with is also credited on the tracks.
Little known fact, but that Janet Jackson song "Together Again" uses the EXACT same melody as a song from one of the Master System Sonic games (second video). These artists/producers are known to have a 'pool' of songs to work from so it is pretty clear the Jacksons and their contacts were involved with the Sonic games. Its not really that surprising when you consider Moonwalker on the MegaDrive/Genesis.
I don't buy the whole "he wasn't happy with the sound output on the Genesis" myth that goes around. Anyone who lives and breathes music like Whacko Jacko would love the sound out of the Genesis (its awesome btw)
Meta data Sonic 3 OST:
Bridge zone from Sonic 1 on Master System:
compare it to Together Again Janet Jackson:
It isn't a case of the "kind of sound alike", they are EXACTLY the same