There is only one big truth about the HF series. The books are a help, a big help if you want, because these are written with as focus the exam, but in the early pages of the HF
JSP, for instance, it's clearly stated that some necessary material for the exam includes the Serlvet spec 2.4, the JSP 2.0 and the JSTL 1.1 specs from Sun. The books are a big help, but these don't cover everything, and the answer to your question is: adapt yourself, don't pretend from the authors the answers to all your needs, and accept human mistakes, as the book has been written by humans likely with very strict deadlines. If you were asked a question that you didn't encountered yet (we all passed through this, believe me) just accept it, and consult the specs to find the answers you need. 99,9999999% of the times, the answers are there.
Good luck with your exam.