They weren't glossing over it.

The majority of people (black and otherwise) look for romantic partners that are much like themselves. That means same race, same ethnicity, same socioeconomic status, same religion, same sort of background (upbringing, culture, values, etc.). There are conscious and subconscious and cultural reasons why it may be desirable for people to do this and it is pretty socially acceptable to only date within your own race (and religion... etc.). Even just mere proximity leads to same race relationships.

The article was specifically speaking about black women who are looking in the dating pool for a black partner (which is probably the majority of black woman) not to advocate black women look elsewhere for partners.