Not every difference has an adaptational reason, but even so; why would blacks need more oxygen to maintain physical performance compared to other races? The brain is an extreme consumer of resources, including oxygen, and in fact cannot break down glucose for energy without it, unlike other tissue which can in some conditions. It is extremely sensitive to drops in the oxygen saturation of the blood. Also, how would protruding teeth prevent airway compromise even if there is more room? There is plenty of room anyway, compromise is more likely to be from the tongue falling back into the throat (when unconscious), a relatively common occurance that would not be related to space anteriorly.
That doesnt mean this is superficial (I doubt it is), but the reductive reasoning of pure adaptation verges on silliness. Of course, with this being a mostly taboo area, the best we will get are probably these speculative biotruths for now.
The worst example of this fallacious reasoning is that gay people were more likely to be protective of the offspring of siblings and become soldiers/warriors as that is the only way they could protect their genes. Believe it or not, I have seen that repeated plenty of times.