.....done in real time (which mean no delays) is needed to recognize difference caused by cables.

The article suggest that:"Taken [cable's effects] altogether (ie., inductance, resistance, interference, skin effect, capacitance), these ugly realities introduce various dynamic and time-related forms of signal distortion which are very difficult to quantify with simple sine-wave measurements. When complex waveforms have their harmonic structures altered [by a cable], the sense of immediacy and realism is reduced. The ear/brain combination is incredibly sensitive to the effects of this type of phase distortion, but generally needs direct, A/B comparisons in real time to recognize them."

I agree with above statement 100%, especially doing it in real time. Any cable testing protocol that is not done in real time and have "delayed" comparison (such as DBT) might indeed introduce human error into testing result, making the results colored.

Also note that article didn't say anything about comparison should be sighted or not

http://www.cardinalproaudio.com/main/speaker.htm