Just my opinion on the inclusion of this on the lists, but I really think it depends on the child's strengths. If you have a child that is more logical than the chance that they question Santa and the Tooth Fairy is higher. I also don't think that a child has to hit all of the things on Ruf's lists. The list is from her dealings with multiple children and not every child she dealt with would be able to fit into that list exactly as she designed it. (I am betting on that!)
Since my DD is still a toddler it is hard to say which level she is at but Ruf's lists opened my eyes to a lot of what we were experiencing. And yet I still have questions on things such as a child that has known her right from her left before she was 2... were does that fall in the levels? My point is Ruf doesn't have all the answers but she opens the door to our thinking about it.