When I slept to set my spawn, after death I spawned at a spot where I died upon spawn. A second spawn after this put me ever so slightly forward onto the world. Right in the corner of 0,0,0. I checked my location with Intyre's hex editor. Any editing of my location or spawn would have me load the world back at the instant death spot. Before I tried the editor I logged out and back in and I found that I will spawn there upon world load.