This is what I understood: I think the software uses the GPS and camera orientation to calculate which way the sky moves relative to the lens. Then uses the camera's image stabilisation to track the sky, i.e. instead of moving the camera, move the sensor.
Yeah, though obviously since this is merely image stabilisation, and not a dedicated de-rotation, there are limits to how far the system can move the sensor and thus to how long the exposure can be.
Eh? The manufacturer datasheet states you can take at most a 300 second exposure with this rotation compensation system, are you arguing this that this limitation isn't a problem?