It is really weird the original study decided to categorize it this way. Especially because there are potentially drastic environmental differences between say the US and Australia. Same goes for the "Other" category. How are China and Brazil similar?

Maybe it's not the bare minimum? Maybe they had limited funding, largely access only to "Western sperm" (which actually is a reasonable category I would argue because we share a lifestyle to a greater or lesser degree), maybe they had sparse data that covered simply "not the West".

If you have sparse data, then maybe you shouldn't be making grand comparisons or trying to make claims about the entire world?

If they had access largely only to "western" sperm then they could separate it out by country, or income, or something more sane. It's not like the rest of the world shares a lifestyle!