Netlist for symmetrical component
Generally, the pin order matters to the model since the order defines what connection goes where. SPICE can tell the difference and treats them differently. However, if within the model it is symmetrical such that the pins are interchangeable, then the external result is manifested as the order not mattering.

So technically SPICE is treating the pins as unique and it is processing it differently in the model depending on which way it is connected, but way the numbers end up crunching out in the model, there is no difference in the end result (for symmetrical components at least. Obviously this isn't the case for something like a diode).