I have seen this left firing first setup on some grouse guns. It is supposed to suit fast incomers, firing the tighter barrel first. Same thing could have been done via reversing the chokes, but maybe it was easier to mess with the triggers, or maybe keep the resale value etc.

It is possible to change trigger positions but the rear trigger may require some bending. Usually rear triggers are bent to center, so the rear blade is in line with the front.