Yep, willemj has been a strong proponent of publishing measurements that are supposed to indicate the be-all-end-all of audio quality. After 17+ years of listening in this hobby, I do not agree with him at all.
The following link was found by another poster when he was trying to find some documentation after I told him that toslink was not as good of a interface as digital coax.
http://www.lampizator.eu/LAMPIZATOR/TRANSPORT/CD_transport_DIY.html
When you read through and get to the measurements of the toslink interface, I thought it was really interesting how bad the toslink waveform was. You would assume that light transmission would be better than electrical transmission, but in truth the LED light emitting diode just cannot "light up" fast enough to keep the true square waveform.
It also shows that not all SPDIF outputs are created equal. lol.