I think the Pinball source code was not included in the leaks, possibly because it was developed by an external company.
From https://web.archive.org/web/20190108095105/https://blogs.msd...
> Cinematronics was founded by David Stafford, Mike Sandige and I in 1994, and Space Cadet was our first published game
> The deal David did with Microsoft was non-exclusive. As Danny noted, we were more interested in the exposure and didn't see much revenue from it. However, it did lead to our relationship and eventual acquisition by Maxis.