Doesn't the USB-C standard already have a well-defined way of connecting an analog headphone, using only a passive adapter? Download the standard and scroll to the end, it's an appendix. IIRC, it can even be used while charging, with the correct passive adapter.
The question then only becomes, is the phone's DAC connected to the USB-C connector, or did the manufacturer omit it to save a few traces in the board? Did anyone test that Moto-Z with a passive USB-C to 3.5mm socket adapter, to see what happens?