It doesn't say that at all. It does discuss differences between two specific groups (out of thousands on our planet), American whites and blacks and even debunks the racist nonsense linked to in the mr_trump subreddit by attributing differences to "caste-like minorities", which immigrants are not (so you don't see the same discrepancy across multiple immigrant generations versus whites in America as you do with respect to African Americans).
In other words, the results of African Americans would not apply to non-American Africans/blacks.
It just shows the harmful effects of multiple generations of institutionalized racism. It's a test for measuring intelligence as American whites understand it, among American whites, applied to a specifically disenfranchised American "caste-like" minority. The American scientific/academic community has seen no worth to IQ measurements or even the test itself in
decades. Might want to move past the 1940s.
These same racist assholes tried to argue Jews were inferior (even to Arabs) a century ago and are now using Ashkenazi Jews to argue blacks, Arabs, etc are inferior! News flash, wouldn't that make white European descendents inferior to Jews? Or Asians? So what is there to be racist about? That whites are the 4th or 5th most intelligent group in your own idiotic classification? Christ...
Btw, there are racist Asian subreddits here where they talk about whites the way white supremacists talk about blacks. It's hilarious, I recommend you visit them.