The level of a car is mostly determined by the quality and type of springs. The springs are what determine vehicle height, not shocks. If you question that, then ask yourself why springs are cut to lower cars instead of changing to shorter springs. That said; worn out shocks can cause sag - a 1"sag? Possible I suppose.
I have an old ford truck that calls for different spring sizes for front driver and passenger side, which is to compensate for battery weight or something like that. Could that be the case here too; where the spring strengths are different? So if you mix the springs up the car will sit wonky?