Automatic Latest Content Deadline Ignored

We have an automatic newsletter that is set to send out every Monday at 5:00AM with the latest post content. It has worked without issue for months, sending around 5:00AM every Monday with the 10 latest posts (or fewer, if fewer than 10 posts were published, or not sending if there was no new content since the last email). This week, Monday, May 14, however, we had no new posts since the last newsletter went out on Monday, May 7, at 5:00AM so no newsletter went out today at 5:00AM. But, when we published a post at 10:42AM today, it sent the newsletter out at 10:42AM today with the new post. From what I understand, this should not have happened, since the Monday newsletter should go out at 5:00AM if there is new content and, if there is no new content, then no newsletter should go out until the following Monday at 5:00AM (assuming there is new content).

Do you know why our newsletter went out at 10:42AM today with our post published at 10:42AM today, instead of not sending today’s email (since there was no new content by 5:00AM today), and instead holding our post published today at 10:42AM for next Monday’s 5:00AM email?

Thank you.