How is the return method used in iterators / async iterators?

How is the return method used in iterators / async iterators?

MDN states that async iterators have a return method

const asyncIterable = {
  [Symbol.asyncIterator]() {
    let i = 0;
    return {
      next() {
        const done = i === LIMIT;
        const value = done ? undefined : i++;
        return Promise.resolve({ value, done });
      },
      return() {
        // This will be reached if the consumer called 'break' or 'return' early in the loop.
        return { done: true };
      }
    };
  }
};

However, the Typescript definitions of async iterators require the return method to

accept an optional value
return {value: someValue, done: true}, whereas MDN does not do this.

Here's the TS definition:

interface AsyncIterator<T, TReturn = any, TNext = undefined> {
    // NOTE: 'next' is defined using a tuple to ensure we report the correct assignability errors in all places.
    next(...args: [] | [TNext]): Promise<IteratorResult<T, TReturn>>;
    return?(value?: TReturn | PromiseLike<TReturn>): Promise<IteratorResult<T, TReturn>>;
    throw?(e?: any): Promise<IteratorResult<T, TReturn>>;
}

Can someone explain the discrepancy? How does return work?

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