Interestingly, even Samsung phone chargers put out 9v, but I think they only do that when connected to a Samsung device. On the plug is says 5v and 9v, and (I'm assuming) they switch to 9v when they detect a device that can use it for fast charging.
It’s called QuickCharge and was a standardized version of Apple’s fast charging or USB C PD many years before USB C was a thing. Samsung was a key player.
The charger emits 5V unless the device supports higher voltage and negotiates it.
