Yes, I have also heard of this being true. Part of it is because it is often rare for a student to get a perfect score of a 7, so teachers refrain from scoring students this high so the IB does not lower the marks of other students if their predicted student with a 7 was innacurate.
A friend of mine recently notified our IBC that he is worried that his paper is too similar to that of a sibling who had taken IB years before. He used his siblings paper to get an idea for a topic. he is worried they will run it through the system and find too many similarities and say he plagiarized. If you get caught for plagiarism is there a certain percentage that it must be for you to have consequences? i.e <15% Also, does the IB notify the college you plan on attending that you were caught for plagiarism?