That article is consistent with my brief legal research, and increases my confidence that Congress has not explicitly prohibited IQ tests by statute, regardless of whether a potential employee could show disparate impact through use of the IQ test. I think this quote from the article is a reasonable statement of current law:

If one reads between the lines of Griggs and all other disparate impact type cases, one may intuit that the real holding is that any moron can do prole jobs such as repairing electrical power lines, and therefore any type of hiring criteria that tends to discriminate against blacks is going to be illegal. But the rarefied world of upper-middle-class jobs are obvious not included.

I make no comment on whether the current state of the law optimizes what it claims, or what it should optimize in some moral sense.