Little help with leaf springs

i understand that.. they should eat the shipping if it was their mistake. my question is why mis match springs?

espo has -1", stock, +1" and +2" springs. eaton sells stock springs and 1"lower springs, there are others out there that i can't think of at this moment but they are matched sets and the car sits as it should with those springs... no need for two of the same side crap..