C# etc. shipping a runtime is a current limitation of wasm and those ports to wasm. But in principle once wasm has GC support they can also compile to tiny binaries.

Not for everything, of course - if you use certain C#/Java/Kotlin features you'll need bundled runtime support. But if you avoid them, you don't.

For comparison, Rust can't emit tiny binaries if you use malloc/free, because it needs to bundle those. This is actually an area where Rust/C/C++ are at a disadvantage once wasm has GC, as GC will be "free" while malloc/free won't be, so many programs will be smaller as C#/Java/Kotlin rather than Rust/C/C++.