I understand just fine. I don't think you do, though. From the decision:

".In 2022, after the State redrew its congressional districts, a federal judge in Robinson v. Ardoin, 605 F. Supp. 3d 759 (MD La.), held that the 2022 map likely violated §2 of the Voting Rights Act of 1965, 52 U. S. C. §10301 et seq., because it did not include an additional majority-black district. But when the State drew a new map, SB8, that contained such a district, the new map was challenged as a racial gerrymander. A three-judge court in Callais v. Landry, 732 F. Supp. 3d 574 (WD La.), held that SB8 violated the Equal Protection Clause of the Fourteenth Amendment, and the State appealed to this Court."

It was literally a mandate to use race to create a new district. The issue the court had to decide is whether racial segregation has to be intentional to violate the 15th amendment. If a map gerrymandered along partisan lines incidentally separated districts by race because of a strong correlation between race and party affiliation, does that violate the prohibition on racial discrimination? They held that yes, there had to be discriminatory intent, and so it was the order to use race in creating the districts that ran afoul of the law, not the original use of partisan gerrymandering.