Okay, but why would you compile JS down to wasm, only to have it then use the browser's built-in JS runtime? I see the use for compiling other dynamic languages, but compiling JS via wasm shouldn't be any different than running it via the normal JS engine, aside from potentially having a slightly smaller executable.

But they will still need to be interpreted ie cpython.

I'm not sure how much space just cutting out the GC will save?

GC is only a small part of a high level language runtime.