I think part of that may have to do with translation and cultural perspective issues. Some of it is because those translating it apparently didn't "get" it. Which is why we initially had the mistranslation where people thought it was Oda talking about "black people being super strong and their afros give them power" which is just stupid.
Oda says "Does the Champ wear the Afro, or does the Afro make the Champ? The mythical power within Afros is a mystery to science even today." Oda is referring to a very specific few Japanese boxers here.
The line is without a doubt a reference and tribute to Yoko Gushiken (left), a Ryukyuan champion boxer who had great fame in Japan, and who wore an afro. He's still popular in Japan, and quite a number of boxers emulate his style as a tribute (right).
He is a major cultural icon, and the imagery associated with him being "a champ" is the core of the reference.