What JoAnn said ^
If she is sending the plant bare-rooted or partially bare-rooted, it makes perfect sense. Plants tend to keep their roots & shoots in balance. They receive chemical messengers that help them decide if it's ok to grow more shoots, or if they need more roots. When you uproot a plant and remove some/all of the soil, a lot of the finest and most important roots are killed and the root system compromised. It then makes sense to partially defoliate or cut leaves in half across venation to reduce transpirational losses so the plant doesn't shed branches or collapse entirely.
Unrelated aside: In bonsai, it's important for us to have the lower branches on trees much heavier than those high in the tree - even while the apically dominant trees tend to want to shed lower branches and concentrate growth on the top. What happens is, the top branches get all the energy and get too heavy; so experienced bonsai practitioners are constantly removing large leaves from the top of the tree or cutting the top back to prevent it from getting too coarse. This is one of the ways we balance energy flow in the tree to help keep it natural looking.
Al