It's called "bluetooth". ?What ever the sensor is called that receives the signal from the remote.
Damn, you're absolutely right. ?I know for sure that the first gen ATV 4k box has an IR sensor; otherwise, my Harmony IR remote and 3rd Gen Apple TV remote would not work with the unit.
4K Apple TV IR Sensor location - Apple Community
discussions.apple.com
I always thought it was Bluetooth as well until I decided to try my 3rd Gen remote with my ATV 4k.Damn, you're absolutely right. ?