Trailing Arm Brushing Question

[conman]

I replaced mine two months ago and they were both on one side. For example if you stood behind the truck looking toward the cab both shoulders were either on the left or right ( i can't remember). I thought it was odd, I was expecting them to be opposite inside or outside. Whether this is right I don't know but I know how mine was, so I put them back the same way. I thought it was do to a torque issue from the diff.