I believe that USB-C is only 5 volts, there is also a commercial version that is 9v, but none are 12/13.5V, which is what almost all transceivers are designed on.
USB-C has multiple modes, USB-PD standard allows many voltages to be used, the default I believe is 5V 500mA but it support 5, 9, 12, 15, 20V and 20v5a for 100w, some devices have special modes upto 40V but those are not USB-IF spec.
They use variable resistance over a handshake to determine the mode and that mode is a specific voltage and amperage.
good read on USB-PD specs on the tech sheets.
STMicroelectronics has introduced two new USB Type-C™ -certified port-controller ICs with built-in protection, which help designers implement interfaces cost-effectively to support their required blend of USB features.
www.st.com
Explains the issues with the resistance, mostly about USB-A to USB-C cables.
What's the difference between USB-C vs. USB 3.2 in terms of transfer speeds and power modes? Here's our guide to clear things up.
www.androidauthority.com