No the claim is anecdotal, much like your claims that Japanese players had overwhelmingly advantages.
The claim that japanese players had advantages is not anecdotal. It's factual. They have lower ping times therefore htey have lower response times therefore they have a higher chance to beat a non JP player to the claim. The difference is not drastic, but any difference at all should be considered unacceptable.

Lower ping is an advantage, whether you like to think it is or not.