In essence, you're right about the fuel pump wiring.
All the Omex sensors in effect operate on the earth side so they are live and the operation opens the earth link.
The process that controls the fuel pump also includes the crank speed sensor.
When you initially switch on the ignition the pump runs as you say to pressurise the fuel rail but after 2 seconds the ECU recognises that the engine is not cranking so switches the pump off again.
However when you then operate the starter and the engine cranks above a certain speed (I think about 200rpm but I could be wrong) the ECU recognises that you are trying to start the engine so the pump keeps running.
If you had a flat battery or duff starter and the engine did not reach the required cranking speed the fuel pump would not operate.
This also means that if for example the fuel line split or detached of course the engine would stop and the fuel pump would switch off to prevent fuel spraying everywhere.
