There is what really happened. There is what people think happened. There are the stories about the event people actually tell.
The three sometimes overlap in small portions. What really happened may be recorded in contemporary documents and materials. All of those recorded items may reflect the perspective of the creator or informant on the record. What people think happened sometimes reflects their beliefs, social mores, and viewpoints–not just what actually happened. What people tell about the event also reflect upon those things but also includes what they want the larger community to think about them and how they want to be viewed.
People’s memories are one of the things we don’t always get. People tell their stories and some informants are more inclined to share their honest recollection of what happened than others. And some individuals simply make honest mistakes.
That’s why genealogists record everything they find, indicate how they found it, and utilize as many reasonably reliable sources as possible.