I don't really see how it requires that the complainant always sues, or that the (is this a word?) complainee prove a case against themselves. All New Haven really would have to do, to win this case, is point to a test that does as good a job of testing firefighting ability and doesn't produce wildly disparate results along racial lines.
And the CSB in New Haven took testimony to that effect. And Kennedy's ruling said that this was not sufficient. Nor was FEAR of action under Title VII sufficient. Instead The City had to actually try and prove that Either the test was biased or that they actually were going to be sued before it could even ENTER into negotiations with those adversely impacted as to what a reasonable alternative might be.
That's a rewrite of the law for which transfers much of the burden of proof from the respondant back to the plaintiff (they have to sue, which means showing standing, etc.) which is the antithesis of the legislative intent. Note that they did not do so because what NH did was "unconstitutional". At least that was their claim. Kennedy's claim was simply that the law as written meant something different.
That's just sill.
Kennedy doesn't want to throw out Civil Rights Law because he's worried about his legacy since he's on his last legs here. Scalia, Alito, Thomas and Roberts very much DO want to.
And no, its not particularly defensible.