I grew up during the time we went from analogue to digital. First thing you learn about digital is that a 0 is a 0 and a 1 is a 1. There is no 0.6 or 0.75. That is the beauty of digital, resilience against signal distortion. To my big surprise however I could hear the difference between a good USB cable (My AQ Carbon for example) and a bad one. But this bad cable worked perfectly for my printer, not a single error ever. I started digging into the USB protocol and found out about bulk transfers and isochronous transfers. Printers and hard drives use bulk transfers. Data is packetized and a checksum is added. The receiver checks the data against the checksum and sends an okay or not okay message back to the sender. In case of a nok okay, there will be a retransmit. So all errors during transport get corrected. At 480 Mb/s the signal edges cause such high frequencies that reflections inside the cable are not unlikely. Reflections can make the USB receiver misinterpret the data bits, but all errors are corrected by the protocol. Modern DACs use asynchronous transfers, the data at the receiver side is buffered and re-clocked with very low jitter into the actual converter. So everything should be picture perfect.
However, for HD audio the amount of data that goes through the USB cable is so high that the bulk mode causes too much overhead. Instead isochronous mode is used. But that is a "send and forget mode", without error correction. So now a good cable becomes important. All errors will be accepted and send to the converter. In PCM data, the 16 or 24 bits, have different weights according to the binary number system. When a bit with a high weight flips, the audible effect will be bigger than when a bit with a low weight flips. For DSD and DoP all bits have the same low weight (little contribution to the signal). So a flipped bit in DSD or DoP is less audible. I am waiting for the first person to stand up and say that for DSD and DoP, USB cables in general sound better than for PCM. While some one is figuring that one out, I will be listening to my music...