Your understanding is technically correct but missing some nuance which is the heart of the matter. It's true the use of an IQ test can be justified. The import

Your understanding is technically correct but missing some nuance which is the heart of the matter. It's true the use of an IQ test can be justified. The important thing is that the use of an IQ test must be justified. Due to the Supreme Court ruling, IQ tests are assumed to have a disparate impact. They are by default assumed to be discriminatory unless proven otherwise. A company must either prove the lack of disparate impact, or demonstrate a plausible connection to work performance (beyond "smart = good"). Most hiring practices are default OK, and a claim of discrimination must be proven in court. This hiring practice has already been decided in court, so it is default not-OK and must be defended. That difference is significant.