The auto arrange is far from perfect. It tries to fit the largest objects in the middle first and then fit the smaller models in the other areas. If you try to print some configuration of objects where the best fit is not to put the first object in the center, it won't ever consider that as an option.
The arrange algorithm that we now have is much better than what we did before, but it's far from perfect. We could improve on it, but as always, it's a resources issue (way to much to do, way to little people to do it with)