Airport Security and the MacBook Air

This past weekend I traveled for the first time with my new 11 inch MacBook Air. 5 days before my flight TSA released a statement saying that the 11 inch air qualified as a small electronic device and would not need to be removed from a bag during screening. With this new ruling in mind I attempted to journey through security without removing my air from my backpack. My journey came to a sudden end however when on both occasions  I was forced to go back and remove my Air from the backpack and re-screen all of my belongings.

While I understand that the TSA reserves the right to ask travelers to remove any item for better screening the troubling thing for me was that none of the screeners had any idea that the new small mac did not need to be removed from a bag. This raises the question, why did the TSA baggage screeners not know about this new ruling? In almost all scientific and engineering professions employees are expect to keep apprised of any new developments in their field. Why then are TSA workers, who are protecting our air travel, not expected to stay apprised of any new developments that affect their job?