IQ is just one number. It would be as silly as evaluating the physical capacity of a person by an average of his clothing measurements. Is this person fat and weak, or brawny and powerful, or wiry and agile? You couldn’t tell it from such a “Size Quotient.”
I suspect that cultural factors have a lot to do with lax mental capabilities in some areas that go into the IQ. And if that can be is controlled for then the races will prove to be a lot closer than this.
... and if that can be controlled for ...