Everything matter in the audio chain. Tests prove it!

Duh. My ears have proven "Everything matter in the audio chain" since I started stereo.  Including power and environment.

All those charts and graphs and my ears still has the last Hear Say,

The room and listening environment have more influence in the sound than cables ever will. You can't fix poor acoustics and/or poor speaker placement with band aids.

Their measurements seem to be done at 11,0dBu level, which corresponds to 989mW on a 8-ohm speaker. Although the graphs are very dynamic-looking, they will fit into a leeway of 0.2dBu, which corresponds to about 40mW on the 8-ohm speaker.

Will that be audible? The author claims it will.

As Albert Einstein said , not everything that counts can be counted.

Technics showed a graph over 30 years ago on one of their integrated amps 

and a pretty clean sign wave, vs a Airtight. Vacuum tube model . And stated Vacuum tube  is now obsolete , sonicly SS equipment at the time under even a bit of distortion was gritty and bright ,where the vacuum tube rolled off with even harmonics and smoother , SS amplification has come along way in 30 years and sounds very musical  , graphs  are good but don’t tell the whole story ,

also your Room can play a huge part of the equation  damping the room of 1st reflections ,bounce reflections ,Bass nulls  treating your room  should be on your short list.

YES and NO!
Not everything can be judged by the tech, BUT neither can you trust your ears. What you like is totally subjective and opinionated at best. Most people have never had the opportunity to sit on a stage with a live jazz band or in a parade with a drum and bugle corps. So you end up with people talking about things being too bright, when all they are noticing is Probably their first experience of hearing a trumpet as it sounds live, or noting the difference between a Steinway vs a Yamaha grand piano. The Tech is there to give you a starting place to visualize what you are hearing and is not meant as an end-all. Also as noted as time goes on, the industry will find more and better ways to present music to our anxious ears to hear.

Anyone going to extremes on wither side of this argument is less than truthful and making uneducated comments.