This should allow for both faster and more efficient wireless charging. The reduced resistance would, at least in theory, allow Apple to increase the power threshold that smartphones can safely handle via wireless charging, without overheating.
The iPhone 8/8 Plus and iPhone 10 can charge at 7.5W. The Qi spec currently allows for a 15W charge. However, if I understand it correctly, implementing a FPC charging coil would necessitate a slight thicker iPhone — and you know how obsessed Apple is with thin products.