This question, about the reasoning of an examiner, was closed as off-topic, apparently because people either thought the example sentence poor English (which it certainly is) or disagreed with the reasoning as identified. Both of these seem bad reasons to close. This is "English Language and Usage", not "Well-written English"; if all poorly-written examples are off-topic, I foresee a severe shortage of interesting questions. And the fact that the examiner's reasoning was flawed and his premises shaky does not make the question off-topic, any more than "why would my boss say this?" would be off-topic at Workplace.SE if the answer boiled down to 'Because he's an idiot'.
I don't actually think the question's worth re-opening, largely because Peter Shor's excellent answer has covered all the important points. But if the question had been closed before Peter got there, an important distinction between 'English you should write' and 'English that will pass tests' would not have been drawn, and a sensible, well-written question would not have been answered. Would anybody care to justify their closevotes?