Comment by zmmmmm

I don't think it's as silly as people are making out. It at least proves a passenger is in control of the device, rather than it being stashed / hidden in the cabin. A device in the cabin not owned by any passenger broadcasting a signal is definitively more suspicious than one with a passenger in control. We don't know what their next step would have been - they might have asked everyone from row X to Y to turn their bluetooth back on to narrow down the search etc. They probably didn't expect that anybody would fail to respond to the first instruction.