Googlers see approved doc in b/300959810

See https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#merge_group which mentions the following:

More than one activity type triggers this event. Although only the checks_requested activity type is supported, specifying the activity type will keep your workflow specific if more activity types are added in the future.

If your repository uses GitHub Actions to perform required checks on pull requests in your repository, you need to update the workflows to include the merge_group event as an additional trigger. Otherwise, status checks will not be triggered when you add a pull request to a merge queue. The merge will fail as the required status check will not be reported. The merge_group event is separate from the pull_request and push events.