"OS – C# is ahead-of-time (AOT) compiled to ARM assembly language. The .NET framework is included, with unused classes being stripped out during linking to reduce the application size. Apple does not allow runtime code generation on iOS, so some language features are not available (see Xamarin.iOS Limitations )."
Normal deployed apps are. Here though, the app that's actually running is the Xamarin Live Player which comes with an IL interpreter. In the normal cycle of Xamarin iOS development from Windows, the DLLs are compiled, and then there's another step where they are AOT compiled to ARM assembly on the Mac. In this case though it avoids the step of compiling on iOS, it just builds the DLLs and sends them to the device.
https://developer.xamarin.com/guides/cross-platform/applicat...