there is a difference between Xamarin and Xamarin.Forms, one thing is just C# => ObjC binding / C# => Java binding (C# to AOT native shared libraries and binds

there is a difference between Xamarin and Xamarin.Forms, one thing is just C# => ObjC binding / C# => Java binding (C# to AOT native shared libraries and binds it into the native things), which basically SUPPORTS ALL of the native features. so basically you can either have one application on top of a custom ui framework (xamarin.forms) or you can only share business logic, and write controllers, which feels native in c# or the native language. i.e. without forms you can build a controller with objc or you can have the implementation in c#, and call into a shared business logic library. unfortunatly the docs are really really weak when you consider what you really can do with xamarin. with forms you can build a ui that works on both platforms so basically you have 100% shared code.