I think the magnet/screen is a wireless receiver, which makes you wonder why would GM put both a wireless transmitter and a receiver in the same box. My theory is that the risk averse engineers at GM were worried about safety risks of someone putting something metal on the wireless charger, even though the wattages are very low. I believe they put in a receiver to reduce the overall output of the transmitter, which is why the 2017s and earlier don't meet the QI standard. That's just a theory--I could be wrong.