If a new phone is sold in India, its Indian owner benefits from the entire multi-year lifespan of the battery before it has to be disposed of. If a used phone is imported from the US to India, its battery will be nearing the end of its life - most of the benefit of that battery goes to the original American owner, but the disposal costs are dumped on India. From this perspective, it's a way for the developed world to dump our e-waste on the developing world and avoid having to dispose of it ourselves.