Are there differing qualities of optical cable?

First, about methodology. Yes, a modern audioanalyzer like a DScope or Audio Precision is indeeed more discerning than even the best human hearing. They can measure subtleties that no human can hear because they are beyond the threshold of human hearing acuity. Think of the parallel with microscopes or telescopes.
As for interfaces and cables, this discussion was about the cables, not the respective merits of the interfaces. If you compare digital interfaces, usb is best for jitter, distortion and noise, followed by coaxial and just after that optical. Do these differences matter? I doubt it, as they are at such elevated levels that no human is likely to hear them (under controlled conditions, of course).