Traveling screeners challenge screeners everyday. Last time I flew out of IAD I even kept a small plastic ruler in my pocket to argue the sole thickness. It wasn't because I wanted to start a fight, but rather my feet stunk in those shoes and I wanted to spare everyone of my foot's wrath. After that flight, I tossed those shoes.

It very difficult for every airport to be in sync with the policies. It's all in how the information gets down the chain that determines how the checkpoint is operated.