So I've tried to contact Kia on FB and talked to them on the phone with no responce regarding that, it says on the Worldwide site that for the 19" wheels setup, you have to get 20 in the back, well that is what recommended, called and checked with dealers around the world and friends from different part of the world and they all told me that the OEM comes in both 19" wheels.
I'm trying to get an aftermarket wheels so I'm not sure if it is recommended to go this size for aerodynamics (not sure why OEM does not follow) or probably just a typo? twice?
that's the website, under Chassis look for wheels and tires and be amazed
Kia Cadenza Specifications | Kia Motors Global Official Site