I don't sit around thinking about how many black and white people I went to school with or what class ranking Asians, blacks or whites have as a group. I just don't. So I was too annoyed to go any further and see whether I would be "humbled" by my unconscious racism.
Judging people on group averages when you have no additional information is called "statistical discrimination", although given how loaded a term "discrimination" is a better phrase may be "statistical differentiation". Statistical differentiation is not racist in that it is not a preference for one race or another, it is simply a decision based on group averages when individual information is not available.
The Implicit Project implicitly assumes that any differentiation between blacks and whites is racist, and does not consider that case of statistical differentiation. This means they do not consider that an individual may make decisions based on factors other than race, of which race is merely a statistical marker.