Do I have a bad revision method or are the tests just ridiculously hard?Watch
I’ve never heard of this though, I always found the text book questions to be ridiculously hard compared to the exam 😅
I would say your method is the problem. Instead of relying on being able to answer the textbook questions make sure you know the content inside and out so that you are prepared to answer anything that may come up.
You expand your knowledge so that you can tackle any question type. Learn the content, thoroughly understand it, try to teach it to someone (even if that person is just your reflection in the mirror), etc. That way no matter what you are asked you have the information in your head to be able to answer it.