> If it really was about calibration, wouldn't you think Apple would've calibrated the screen at the factory and programmed the controller with the calibration data?

That sounds like a process thing that could go either way. I can imagine a system where they wait until the ipad is assembled and then use the hardware on the ipad to run the color calibration against the screen being simpler/more sensible to integrate into production than a system where panels need to be plugged into a separate thing earlier on.