I was reading people's comments about York bars and stumbled upon this golden nugget. The venerable Bob Hoffman might have had an opinion or two for you on this one.
Anyway, who gives a shit? What good is the answer to this question gonna do for the majority of us? None in my opinion.
However, I wouldn't be so quick to say technical proficiency is not a component of this success. Proficiency is not perfection. All world class sprinters are technically proficient even though their individual anatomical differences often throw a little "signature" into the kinesiological mix.
Racist thinking or not, it has been established that genetic (yeah, yeah as well as socio-cultural) factors are largely responsible for this difference.
All coaches can do is stay abreast of the lastest developments in sports training and thank god when they get a white athlete with the "right" genetic mix a la that kid out of Baylor University who won the Olympic gold in the 400 meters.