Those really make my phone overheat, so I avoid them. Didn't they heat yours up?
The only time my phone has given me a message about heat was, indeed, in a phone holder in the car, but it wasn't even charging. We are experiencing a heat wave in Australia right now though, and the car had been sitting in the sun in a car park for an hour.
But, I figured that the battery would heat up more the faster it's being charged, and so wired charging at the same wattage would heat the battery more than wireless charging.
Must be a lot of power->heat transfer loss with wireless charging.
/s