If I recall correctly, PB said GW makes cross-platform gaming absolutely possible, it's the rights and licensing parts that are the issue. Regardless if S3D is behind the Xbox One backwards compatibility, I find it incredibly interesting Microsoft accomplished it through emulation.
"I asked Microsoft officials for more information about the emulator and was provided with this statement by a spokesperson:
"What we did was essentially built a virtual Xbox 360 console entirely in software. So when you launch a game via Xbox One Backward Compatibility, you'll see that the game first starts up a virtual Xbox 360 console, then launches the title. The work is ongoing as each title requires individual packaging and validation work to enable that virtual console capability, but we're committed to continually rolling out new titles each month."