Joel Spolsky said it best here:
http://www.inc.com/magazine/20070501/column-guest.html
To quote:
"When you fill an opening, think about what happens to the 99 people you turn away. They don't give up and go into plumbing. They apply for another job. There's a floating population of applicants in your industry that apply for nearly every opening posted online, even though many of them are qualified for virtually none of these positions. "
The article's author is assuming that the people in the under 6 months and over 6 months are identical candidates just based on resumes. They are ignoring all of the "soft skills" that can get picked up in actual interviews.