The fuel nozzle is a completely mechanical implement - there's nothing electronic about it, and the pump has no idea whether you are manipulating the trigger or using the hold-open.
Because it's mechanical, however, the way the hold-open is designed needs to allow for further actuation of the trigger mechanism to free up the hold-open lever when your tank is full. Because of this, the highest setting on the hold-open is less than the full actuation of the trigger mechanism.