Well, when it's based on a true story, there's a sense of connection to the real world. It can serve as a historical record or a way to understand a particular event better. Fictional aftermath stories, on the other hand, are more about creating an interesting narrative. In 'Aftermath Based on a True Story', the facts drive the story, while in fictional ones, the plot devices and creativity of the writer play a bigger role.
The main difference is the authenticity. 'Aftermath Based on a True Story' has real events as its foundation. Fictional aftermath stories are created from the author's imagination. So, the former will have more real - world details and consequences that actually occurred.