It's not a native desktop app either, it embeds a large JIT and a hello world is around 50 MB.

This might be my lack of knowledge in this area since I'm just reading at the minute but from my reading that's not the case. If you create a standalone app (exe compile option) there is no JIT, just: "A standalone, architecture-specific executable file containing the source code compiled to machine code and a small Dart runtime." that "... handles type checking and garbage collection."

Unless that runtime is what you're referring to as a JIT. But since it outputs machine code that is a compiled program, not a JIT. I obviously can't speak to the size as I've not written anything yet, I'm just practing.

Quite happy to be corrected if I'm misreading things though.

You seem to be a bit confused on this topic. Have you actually used Flutter before? What you’re describing isn’t how it works at all.