Exposing a "thenable" can be ~2 times slower than exposing a promise directly

createDeferred.mjs

void async function() {
  function createDeferred() {
    let resolve, reject;
    const promise = new Promise((...args) => [resolve, reject] = args);
    return Object.freeze({
      resolve, 
      reject,
      promise,
      then: promise.then.bind(promise)
    });
  }
  
  console.time("deferred");
  for (let n = 0; n < 20000000; n++) {
    const d = createDeferred();
    d.resolve(true);
    // ~2 times slower than `await d.promise`
    await d;
  }
  console.timeEnd("deferred");
}().catch(console.error);