I assume that you are refering to the USB C connector on an v2 ASIAIR, right? You hadn't mentioned which product.
A USB-C connector is simply a physical interface.
Electrically, the pins can be used to perform a number of different standard functions, like power for charging devices, power delivery (PD) for auto sensing voltages, Thunderbolt devices, displays, and yes, it has also been used as the physical connector for a USB-2.0 and USB-3.0 interface. An ASI mini-camera uses a USB-C connector for its USB 2.0 interface, for example.
In this case, if you mean the ASIAIR product, the USB C connector in question is simply a way to supply 5V power to the Raspberry Pi 4. (The Raspberry Pi 3 (v1 ASIAIR) uses a micro USB connector for this purpose.) There is no Thunderbolt interface, there is no USB-2 or USB-3 interface on that connector.
Do not apply power to it unless you first remove the daughter board in the v2 ASIAIR. You will fry something, and it might not just be your power supply or the daughter board.
Leave that connector alone!
Chen