Two iPhone connections?

It is my understanding that the Bluetooth in a 2013 with the tech package would allow two concurrent phone connections with either phone being able to receive calls but only the primary being able to place calls. While driving with my wife today she got a call on her iPhone 4s but it did not come through the Bluetooth. When I checked the Bluetooth connections it showed my iPhone 5s was connected but showed hers as paired.



What am I missing or doing wrong?



Thanks.