Indeed, in my SCJA Certification Guides, I don't mention how many answers are correct, only that it is either a single answer (radio button) or multiple answer (check boxes).
HOWEVER, the actual exam tells you how many answers are correct. That's a trend I've seen for every cert exam I've taken, even from IBM. I actually had an IBM question once that had four options, and it told you that four options were correct. Obviously they hadn't proofed that exam too much.
Whether to put the number of correct answers into mock exams is a decision that isn't made with haste. Most writers I've found have agreed to opt out of putting the number of correct answers in to try and really make the student think about the options they are selecting.