I think the article is saying that the decision whether or not to audit is not a function of race, but black people are more likely to file certain kinds of ret

I think the article is saying that the decision whether or not to audit is not a function of race, but black people are more likely to file certain kinds of returns (eg with earned-income tax credit) and those kinds of returns are more likely to get audited because they're more likely to contain mistakes. I wouldn't call this "racial bias" at all.