Either they are very slow learners, or I am.

The incidents which prompted the (ahem) article were in-flight discovery of water and bomb threats (note and phone). So what were these phantom terrorists probing ? How to openly display a smuggled bottle or how to force the evacuation of a plane ? Somebody explain to me a scenario in which either would conceivably be of use in a planned attack, the object of which is slaughter and mayhem. In simple words if possible.

There may be casing going on, but this wasn't it. There may be another attack, but the TSA won't foil it.