Here, the prompt instructs the workers to make sure the new 'wrong ending' sentence makes sense standalone, that it does not differ in the number of words from the original sentence by more than three words, and that the changes cannot be as simple as e.g., putting the word 'not' in front of a description or a verb.
the workers had much less flexibility for changing the underlying linguistic structures which can help tackle the authorship style differences between the 'right' and 'wrong' endings.