The ST-LINK/V3-MODS product pages list UART under the supported BRIDGE modes. The API pages do not implement any access to the UART interface.
I know that VCP is an option, but unified access through the API is a large benefit when controlling multiple interfaces (i.e. GPIO) to make sure to controll both interfaces on the same device. With a (V)COM port you can never be sure if the UART belongs to the same board as the GPIOs do.
