The thing is, in order to do the "extract the guitar bass drums from a single track mono recording" trick, you're talking pretty arcane stuff and it's not perfect.

I haven't heard this myself yet, but from what I've read, the tracks don't sound like fresh clean stems from a multi-track tape. The resulting arcanely-separated tracks sound kind of thin and still have remnants of the other instruments in them. It's only when they're added back together that they begin to sound like a proper recording again. This works fine for the Rock Band game, where your goal is to make it sound like the bass dropped out when your bassist makes a mistake. But for an audio recording purist who wants something he can truly remix as if he'd had original stems, that's not going to be available.