Let me try wording this differently for you. "What if I develop something with only local calls between my front and back ends, and later I decide I want to test/implement a front-end feature on Android/iOS which doesn't support running the back end. Do I have to change my development so it is no longer local?" - the answer is yes.

On the other hand, "remap my whole localhost development" is a REALLY impressive-sounding way of saying "change the one line in the config file that says to connect to 'localhost' to connect to 'api.myhost.com' instead." Or maybe, if you are a sloppy developer, "use search-and-replace to replace all instances of 'localhost' in the code with 'api.myhost.com'." Either way, it is a trivial change.