The spring spans the same (total) distance front to back regardless of whether it is properly placed or reversed. So, in that regard (total) distance is not a factor. Now, that said the through bolt on the front of the spring is larger than the rear. So, someone would have to use a smaller than original bolt in the front (not ideal) and would also have a loose fitment in the rear because the through bolt is too small. So, yes, with sloppy fitment the springs can be installed backwards (and even upside down for that matter). Neither should be done, but it is possible.
There is a rear end locator associated with the spring that is more forward on the spring than rearward. Therefore if the springs had been reversed (and the rear end still aligned with the locator) it would have moved the rear axle backwards and out of the center of the wheel opening. What I could not tell him was how far back because I have a wagon and the spring length is longer. Thus if reversed the measurement with a wagon spring would have been different than a non-wagon.
The problem was his rear rend was located too far rearward. We were trying to determine why. Thus it was feasible that the spring being reversed was a possible cause.