I haven't met anyone who can hear digital cables and but a handful of people who can demonstrate that they can hear analog ones.
FWIW, I'm very skeptical on this issue. I know a guy who runs short SPDIF patches on pro SBDs with a twisted pair. (which is ~75 Ω, but unshielded)
I'd love to see it quantified with lost bits, or recovery algorithms being engaged on hardware, or something else quantifiable.
Interesting that you hear a clock. I'd love to see an analyser on the two bitstreams to see "what's happening."