Currently, the article summary is generated provided the article contains at least 150 words. So when articles with fewer words are created, the article summary is shown empty.
Practically, this is a poor user experience (as the end users wouldn't understand the limitations) and also real estate waste.
In those articles, if the article summary space is removed when the criteria aren't met or if there is a toggle to switch the summary off for specific articles, it would be helpful.