Seems like a gimmick to me.
In a nutshell this has the same limitation has Xamarin.
The Business Logic is shared , but the UI Logic and the Technical Logic aren't shared or not completely.
The Xamarin community has been struggling with this issue for half a decade and they ended up re-writting their own rendering engine[0] (similar to Flutter) in C# on top of Xamarin to obtain truly MVVM Cross-Platform Framework.
My point here is very simple , getting Kotlin to run on iOS is great, but it's somewhat a waste of time because of how much time and effort it would talk to create a Runtime or Rendering Engine to normalize UI/UX on differents platforms.