You'll find that my exams are very close in difficulty and scope to the real exam.
When you're running out of ideas for mock exam questions, it's easy to stray from the objectives and put in questions that are harder than anything someone will see on the real exam. I'd hazard to say that is what you're seeing in the WhizLabs quiz - the question writers having a hard time coming up with enough questions, so they stray. There's nothing wrong with 'overstudying', but yes, I have seen these types of exams disparage people, as opposed to giving them the confidence they need to pass the exam.
I also have a book of exam questions available that has over 350 questions not listed in the
SCJA certification guide. That's extremely representative of the exam, and many people have told me that going through those questions was the difference between passing and failing for them.
Best of luck in your studies!
-Cameron McKenzie