What are the two flaws?

I think the first flaw here is assuming that each individual question will be hard just because the exam as a whole is hard. It's possible there are a few questions that are softballs on an otherwise hard exam. This is a part to whole flaw. The second flaw is that the author takes relative difficulty to mean absolute difficulty. The author here says that one thing is harder than the other. But this doesn't mean that it's actually hard. It's possible the other exam is just insanely easy.