However some adapters may also work by having a built in dac instead receiving digital audio

The simple adapters which dont provide power to a phone often work differently from this using whats known as audio accessory mode where really all they do is take analog audio out of the phone

Since there is no such mode in usbc as audio accessory with upstream power devices like this are forced to be data devices appearing as usb peripherals being what wed often call a sound card audio interface or dac