[cwilbur]

Here's your fundamental problem. It's a logical fallacy.

You observe that a good employee is likely to have a high IQ. From this, you conclude that a bad employee is likely to have a low IQ, and that a person with a high IQ is likely to be a good employee.

The truth of a proposition does not imply the truth of the converse of the proposition (A - B does not imply B - A) or of the contrapositive of the proposition (A - B does not imply !B - !A).

Further, no company has a verifiable screening program, because they can't evaluate how good the people they screened out were. Suppose a company has a screening program that rejects 90% of candidates completely at random. They then choose their hires from the other 10%, using other means. As long as they get good hires in sufficient quality and quantity, they will believe that the screening program is effective. They have no way of evaluating the people rejected by the screening program.