It works in both cases (false and true). I'm unsure what WebRTC version is implemented in the browsers (to look at the API docs). Unsure how this is implemented but in js:

```js
var func = function (a, b) {
  console.log(b);
};
func(1, 2); // logs `2`
func(1); // logs `undefined`
```

It is unlikely, but possible, that the implementation looks at the arguments array.