Cameras don't always move around 0,0,0. If I need my object off center, this speeds things up. If you want to match 5 different backplates, this allows you to leave your object where it is, and leave it alone.
Scale is also important. Fspy handles it in a pretty simplistic way. You choose one axis at the origin drag the handles, then type in that distance. You can usually find Something in an image that you can make a pretty good guess at the scale. Floor tiles, someone standing there, a car wheel, chair, counter. There's almost always something.
If you set those things for each camera match, you won't have to adjust your model at all.