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

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.