On iOS, the mobileNetworkCode and related fields always return information based on the SIM installed in the device. This means the actual network code that the device is using is not available.
On Android we have a choice between getting the SIM or the actual network MCC & MNC data. The SIM and network code are different when the device is roaming for example.
To be consistent between the platforms, the functions will now use the SIM information exclusively on Android.