The "deal" is that large, men's shoes, particularly those with steel toes etc look like "questionable" items to someone checking the xr-ays of the luggage. If they question something in your bag (namely what is that shoe?) they can check it out quickly and easily if it is on top.
They are lookin for (among other things) explosives and weapons. That is the reason for the x-rays.
I have a shoe fancy. Seven days means 10 pairs of shoes. I cannot imagine why anyone would be packing sandals and slides on top? They work perfect as cushions in the bottem of the suitcase. Prevents wrinkles.-J