I'm curious, what amp is this? Is it for charging something? The end is TRRS, is there a DAC/ADC molded in the plug for audio interface purposes?

The amp is this one: https://www.amazon.co.uk/dp/B098JTSJTH

As far as I could tell the cable is dumb. If you plug the cable into a regular USB-C socket (which I do not recommend) then the tip is +5V and the rest is ground.

In fact it's designed to plug into the plug marked "mobile" on the amp and the 3.5mm end goes into the line out of something else, providing AUX input, which is mixed straight through to the output of the amp (which is thankfully a regular 3.5mm headphone jack).

I guess they over-ordered USB-C sockets and decided to yolo it, or else for some reason only USB-C footprints fit into the space on the PCB. (But they still had to manufacture or were able to obtain these cursed cables ... it doesn't make a lot of sense.)