Your article it out of date. Racial gerrymandering is the one kind of gerrymandering that is not allowed according to the supreme court[0]. Representatives will go out of their way to argue that their gerrymandering is purely partisan because that's totally legal – for now.
That is incorrect. The Supreme Court's decision is with respect to "overconcentration" of blacks, in a context where, when divided, they were able to elect their preferred candidates. Their guiding principle is still that blacks must be neither diluted enough to make their votes irrelevant in "their own" areas, nor concentrated enough to make their votes irrelevant outside - as the dissent notes, this itself amounts to a racial gerrymander (you don't get to club yourself in the head when drawing district lines and "forget" that certain areas are heavy in both blacks and democrats). They did not overrule Gingles, they cite the state's action as contravening it.
Unsurprisingly their jurisprudence on this is a shitshow as they try to square this circle while pretending like it is some sort of neutral antidiscrimination provision while also attempting to secure a minimum threshold of black political power.
[0] http://www.motherjones.com/politics/2017/05/supreme-court-no...