Historically iOS applications have had a number of limitations when running on a device, as Apple disallows the execution of dynamically generated code. Applications are compiled “Ahead of Time” (AOT) before deployment because of this. You can read more about this architecture here.
Important changes are coming to watchOS! Checkout our support for Apple Watch Series 4 new processor architecture, ARM64_32 based on the Xamarin.iOS SDKs shipping with Visual Studio 2019 and Visual Studio 2019 for Mac.