I do have a few related thoughts on some different points in the article.
> The ideal extraction yield for coffee is between 18% and 22%. An under-extraction of 15% or over-extraction of 25% will cause an imbalance in the components and will result in either acidic or a bitter-sweet coffee drink.
The lower bound of the range is accurate, but the upper bound is outdated. People like Scott Rao and the folks at Barista Hustle have been involved in expereriments to push extractions even higher than that; if I recall correctly, I think they've reached just shy of 30% while improving the taste of the resulting coffee. The key is that bitter flavors don't simply start extracting past 22%, but that above 22%, the _evenness_ of extraction becomes very important. This is the point where factors like the grind size distribution (from the specific combination of beans, grinder machine, and burrs) and technique (e.g. your method of hand pouring to avoid fine particles from clogging the filter) really start to matter. Bitterness can even occur at 18% extraction if the grind size distribution is very uneven.
Another related detail the author mentions is that the second and third re-brews result in more watery cups. This is partly because fines (the tiniest particles) in suspension are major contributors to the texture of the coffee beverage, especially for espresso. Once you've extracted most of them in the first brew, there won't be much left for repeated brews.
My angle on this is that this is not a useful technique unless you're intentionally trying to ration coffee. If your repeated brews seem to extract some additional good flavor, you may want to explore ways to increase the extraction from the first brew instead.
On a related note, there is an old invention that essentially constantly rebrews coffee: the percolator.