Wiki has Neurotica listed as just Jon and Richie. But it also has Thank you for loving me's cowriters completely wrong so I don't know.

I don't recall ever hearing Supa was a co-writer on OTSG. If Supa co-wrote both Neurotica and Too Much Of A Good thing I don't know why it's far fetched to think the three of them wrote them together the same way Jon brought Richie into writing with Billy, Richie bringing in Supa isn't crazy. IF he indeed co-wrote one to say goodbye they could have all been written in the same session.

Supa's press releases wouldn't have much reason to mention working with the band if the only thing that came of those songs are buried on a box set and the bonus track of an album. His work with Aerosmith and Sambora actually made the albums.

EDIT: Apparently he co-wrote Ain't No Cure For Love as well.