> For instance to run on in Swift on iOS, it has to compile to native, and then it wraps it in a C interface and finally in a Swift interface. This has absolutely nothing to do with Gradle.

And what exactly orchestrates the process of compilation (invoking Kotlin compiler + fetching dependencies)?

Whatever you want, really. The default just happens to be Gradle because that's the default on Android.

My point is that the fundamental difference between Flutter and KMP is not at all Gradle.

Last time I checked, Flutter was relying on messaging. KMP leverages FFIs. Flutter is a framework, KMP is not. If all you see is the command line you invoke to run the build, I think you're missing a lot.