Trouble with any such testing is, no two syncs, even with the same cable and minutes apart, are guaranteed to be exactly the same. It might depend upon whether the central heater stat has kicked in, or whether radio 4 is broadcasting laughter or silence, or what direction the radar station at the local airbase happens to be pointing, or dozens of other random factors.
I would argue any tiny differences that might appear to be attributable to cables are pretty much indistinguishable from these random factors. You can reduce the random effects by doing enough tests that the random stuff statistically cancel out, but DLM would spotted all the disconnects, and would have intervened long before you got to that point - ruining the experiment.
On the odd occasion I have tried to do any such testing, I have found no solid evidence that posh cables make the slightest difference.