Let's say that a man has a subscription to The New York Times, but the NYT chooses to print a Men's version that has some job postings and a Women's version that has other job postings without telling you. What if the man is a cosmetologist and isn't seeing any cosmetology job postings because they're all in the Women's edition? The issue with targeting by sex is that it presupposes interest in certain areas, and while a person's interests can change, a person's sex can't [without significant medical intervention].