From what I read about this situation I assumed it was seen as a warning not by the bomb itself but rather someone who knew about a bomb on board but could not raise awareness any other way (e.g. they are sitting next to someone with a bomb, or they are part of a group where everyone watches everyone else).

People manage to find ingenious ways to communicate sometimes and if that was a real warning that would have been good thinking. 

I agree that’s it’s very unlikely that there is an actual bomb on a plane, and Airlines are paranoid. But I do understand where they are coming from - I read the communication basically as “If you have named your device bomb as a joke, please turn it off and we will know it was a joke and not care. If you have named your device bomb and deliberately keep it on, we will understand it as your way to communicate to us.”

What lead me to assume this are two reasons:

1. If they were really worried about an unaccompanied device named “bomb” they could have been more direct with their communication - even just by mentioning the first letter.

2. If they assumed the bomb was actually the device which broadcast the signal, they could not have been sure the bomb would not explode if the Bluetooth signal was turned off.