[BizarroLand]

I feel like that is why the article writer said it got them 80% of the way.

Pareto's principle indicates that the biggest 20% of work will provide 80% of the expected results, whereas to get the last 20% of expected results will require 80% of the work.

Doing a basic room EQ with the equipment you have on hand would mean that the spot you EQ'ed from would have a listening experience calibrated to the quality of the microphone at that location (but with a margin for error since they were not using any heuristic other than "make line as flat as possible in a single pass")

That's ~20% of the work in making a pristine audio environment but with close to 80% of the end results. Room correction, reverb baffling, bass traps, better speakers, fancier receivers with complex auto balancing algorithms all could definitely improve the end result but will take far more time and effort (and money) to achieve any noticeable improvement.