A lot of what Disney is doing is slowing down the line so that the real security can get a good look at everyone. It has long been said that most of their security we don't know about. Which is true of many places. If you know what security measures are in place, you can take steps to circumvent it.
They pick up the bag from the bottom to feel the weight of it, btw. And being inconsistent is the best thing to be.
Slow the line down, they do a great job of that.