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..
That's what I was saying to them..I know from what I understand it is better for a drag car..but the are heavy duty for my 8³/4 rear. Just wanted it to sit correct..and I want it to turn same left and right turns..and from what I read you want the same spring..so hopefully they do me right..