AirPods has a sensor to know you're wearing or not. Just wearing it will connect it to your devices. (Connect, not pairing. You don't have to "pair" AirPods anymore)
I understand how they work, just using the old Bluetooth term. I don't have to pair my Bose either since their are already "paired", they connect when I push the button.
Also, they have to "pair" at least initially or they would connect to any iPhone in range. Pairing is the association between the earphones and the device. It may not "pair" in the traditional bluetooth sense, but it still pairs.