Sounds like the same question to me, for sure the students intended it that way. Many hard problems feel like you need an internal mental SAT solver to arrive at the solution.
Anyway, even if it were an invalid question, his answer still does not make any sense.
Those are definitely not the same question, NP-hardness has a precise meaning while "hard to solve" is a subjective judgement
The answer is trying to show the absurdity of the question. It's like asking for the time complexity of factoring 120. If there is no input to the algorithm, the answer is always trivial.
Anyway, even if it were an invalid question, his answer still does not make any sense.