What BS from Phil Spencer. Full scene ray-tracing is the biggest step change since the 2d to 3d transition (the recent NVIDIA demo with transparent beads come to mind). All that tells me is that the upcoming consoles are severely lacking in the ray-tracing department.
Maybe the fact that in the demo you mentioned your “playable character” is a marble rolling around in a very pretty and very static environment should give us an idea that expecting that level of realism and RTRT in games with all sorts of other technologies, animations, dynamic objects and environments, is not going to be easily attainable on consoles or even super duper Nvidia hardware. Hence, Minecraft RTX.