I just skimmed through the article. I might read it completely to get a better feel for the authors specific point, but I do think his conclusions is a bit of a stretch.

Application Analogy: You have pain and need a pin killer, the instructions tell you how many pills to take. On the instruction there is a chart for age which is suppose to correspond to weight, and it tells you <12 take 1 pill >12 take 2 pills, <8 see doctor. The problem is there are some very big kids and some very small adults. Basically the bodies are lumped into 3 basic sizes Small, Medium and Large and then average weight is plotted when determining an application needs. The purpose is create an easy way to apply quantities to a lot of people. It is basically a short cut.

It looks like the Author has done the same sort of thing. You can't really lump bodies and part sizes into specific weight-classes no mre than you can apply age to weight-classes. So Pacquiao has a large wrist size, well... I'm not sure you can take that and say he is a natural 147 lbs fighter. Most fighters his size fight in the lighter weights. Fact! not analysis.

Some averages:
Heavyweight : >6'-0
Cruiserweight: >6'-0
Light Heavyweight: >6'0
Super Middleweight: 6'0
Middleweight: 5'11
Light Middleweight: 5'9
Welterweight 5'8
Light Welterweight: 5'7
Lightweight/Super Featherweight: 5'6
Featherweight: 5'5
and smaller....

(Although there are some guys that can qualify for the lower weight class being much taller.)