The most accurate answer to the question is:
Yes, there is no acceptable score in Turnitin – students must check over all of their citations to ensure they are correct.
While a lower originality score may suggest a lower likelihood of plagiarism, it does not automatically mean that plagiarism has not occurred. It is the student's responsibility to ensure that all sources are properly cited, regardless of the Turnitin score. Submitting a paper with incomplete citations can still constitute plagiarism.