If I am correct Flutter compiles to Dart code which compiles to Native code.

Above I was more talking about platform integration. As Flutter their own document states everything within Dart is compiled to run like its own enclosed runtime environment. It talks with the native world with messages over channels.

https://docs.flutter.dev/platform-integration/platform-chann...

Within Kotlin however it is possible to directly call the native method. So it looks like Flutter has more overhead for native communication than Kotlin.

Here for example a part of a C interop tutorial in Kotlin. You can directly work with data coming from C libraries.

https://kotlinlang.org/docs/mapping-primitive-data-types-fro...