I think you need to look up how their "match %" is computed. It was described in an earlier post on that blog.
"All OkCupid users create their own matching algorithms, so when we determine who matches who, we’re just crunching the numbers people give us."
Aspects like age/location can be included as part of the user matching algorithms if it is important to them. Overweight/has kids/ugly should be equally spread out between races and should not be dependent on race, especially only after the first message.
Therefore match % is basically everything except race that is important to the user.