Let me ease your mind a little.
No one has the language on the cuniforms figured out 100%.
They disagree with each other on what some of the symbols mean.
So they put together the pieces the best they can, and guess at parts they are not certain about.
And thus, the stories vary depending on who is interpreting the language.
And, just so you know, just because the cuniforms have survived and can be dated does not automatically make them the original text of the story.
Earlier texts could have been written that did not survive or have yet to be discovered.
So, don't believe everything you read.