Twenty years ago, it was common for tire companies to publish data on rolling resistance and other performance factors. But, the chart in the article was the first multi-brand comparison I've seen in many years.
The results were similar to what Schwinn found in tests back around 1970...two tires of the same size and weight may vary in rolling resistance by a factor of two to one...yet there is no easy way for a customer to find out that information.
The chart in the article seems to have been done by Continental, which is interesting, because Continental tires did not get the best results in the tests.
Tests done twenty years ago showed, not surprisingly, that many 28mm tires outperform some 23mm tires, plus have a "plush" ride, last twice as long, and have twice the flat resistance.
The bike industry responded to the evidence that 28mm tires are the best size for non-racing purposes by designing frames and forks that make it difficult to use 28mm tires, and impossible to use 28mm tires with real fenders.
The pros use 23mm tires, so the other 99% of us are supposed to use them too.