A lot of the fastest 40 time guys are small and/or skinny and tend not to hold up in the NFL. WR John Ross, he of the record breaking 40 time at the '17 Combine is a great example. RGIII is another. And there's always a slew of slow black safeties and CBs who are drafted high anyway, the idiot safety on the Saints who allowed the Vikings to score the winning touchdown being a great example of that.
The relatively few legitimately very fast black guys is shown when they get in the open field and put distance between themselves and their pursuers. Almost all White players can hang very well with the great bulk of black players who play the same position speed-wise on the playing field, and of course there's some legitimately very fast Whites too, and on average more quick ones.
Another curiosity I've noticed is that when you look at the 40 times of linemen, tight ends, linebackers and quarterbacks, it isn't noticeably black-heavy at the top; there are Whites and blacks mixed pretty well from the top to the bottom. So if Whites are just as fast at those positions, why all of a sudden is it that they aren't as fast on average at receiver, cornerback and running back? It goes back to the lack of White participation in sprinting and the way White kids are racially slotted in football beginning at an early age away from the speed positions, and the tendency of many fast White kids to take up sports like lacrosse, baseball, hockey and others seen as not being black dominated, all the reasons and more we've discussed over the years.
