`browser.storage.local.set` Promise doesn't wait for `storage.onChanged` listener to fire

Add-ons Development
#1

I would expect when I await setting new value to the storage, all onChanged listeners has fired. But it doesn’t work in Firefox, but it seems to work in Chrome.

Is this a bug?

Example code (can be executed on any add-on page console):

(async () => {
  let text = '...';
  browser.storage.onChanged.addListener(onStorageChange);

  console.log('EXPERIMENT: before', text);
  // we await setting new value - this will trigger "onChanged" handler and mutate "text"
  await browser.storage.local.set({experiment: Date.now()});
  // text value should be changed now
  console.log('EXPERIMENT: after', text);

  browser.storage.onChanged.removeListener(onStorageChange);
  
  function onStorageChange(changes) {
    text = 'text mutated!!!';
    console.log('EXPERIMENT: onChanged', text);
  }
})();

EDIT:
It works in ESR 60, but not in 66, 67, 68, 69. So it does sounds like a bug…
EDIT 2:
I’ve reported a bug.