What does a server seeing the address have to do with the app seeing the address directly from the OS? The app knows the address it needs to talk to, so it preps the message and then calls an OS provided method to make that call. The OS method then returns the response. The app never needs to know the IP address of the device on which it is running.

It does not, but it will try to grab it anyways for the purposes of tracking. Given that this is trivial to get there is no reason to hide it from apps.