Dude, I was _in_ the team that would have been responsible for providing some of the compatibility layers to make such a thing possible. Code to do that wasn't even on our horizon when I left. Added to the fact that running a single game through BC testing (from Xbox to 360 days) takes about 40 hours on average, we're talking 4 man years of work or more. In the 360, we accomplished this by hiring hundreds of outside contractors to plod through the games. There is no way in hell that the Xbox team would do that at this point in the development cycle, it's a security nightmare.
So, unless multiple teams got retasked immediately after I left, and MS disclosed a significant amount of info about an unannounced device to hundreds of low-payed individuals not known for their discretion, your info is bogus.