If I remember correctly, older versions of the OS displayed a warning that calls might interfere with USB 3.0 data transfers. I suspect newer versions of the OS simply put the phone into Airplane Mode when USB 3.0 is enabled to avoid the interference.
I read a post somewhere about how the SD Card is also disabled when USB 3.0 is enabled. In that post someone mentioned that the SD Card is on the same hardware bus as the USB 3.0 controller and the USB 3.0 controller requires the entire bandwidth of the bus in order to operate at USB 3.0 speeds. I suspect this is the same reason USB 3.0 would interfere with calls and other functionality. This is a design limitation courtesy of Samsung.
Unfortunately, this means that USB 3.0 data transfers are only possible while not using the phone for any other purpose.
I certainly hope that future phones with USB 3.0 support will use a hardware bus with high enough bandwidth to support USB 3.0 data transfers without limiting phone functionality or place the USB 3.0 controller on a dedicated bus.