iPhone doesn’t have the feature like “mock locations” as on android, so it will depend on the app you are using. I tried broadcasting my M2 over Bluetooth and connecting to it in the PIX4DCatch app, but it wouldn’t detect it.
Agreed, there is no reason why the PIX4DCatch app can’t receive gps position over Bluetooth NMEA. But the developers need to make it work. I was hopeful because the app stages “RTK Bluetooth receiver” and doesn’t specifically state on the ViDoc, but it seems it only works with their hardware.