That's fine in a language with a bunch of implementations, but JS only has one (relevant) implementation.

V8 powers Chrome, all Chrome-based browsers (Brave, Edge, etc), node, and deno.

Sure, you can switch your backend to some esoteric thing based on Rhino, but unlike C/C++/whatever, your end-user's also have an implementation and it matters. And they are overwhelmingly using v8.

The Ecma International is basically naval-gazing at this point. They don't control JS, google does. Just see what happened when they added TCO to the spec and google didn't implement it.