I always took that Santa Clause/Tooth Fairy idea to mean when the child first realized that it might not be likely to be true. You could tell DD9 had kind of figured it out at 5, but the idea of it bothered her so much she was very conflicted about it. I think she still wanted to believe and didn't want to deal with the reality of the fantasy, IYKWIM...
I also think there was a fair bit of strategy involved, IE, if they know I figured it out they might not get any more stuff,or at least as much, LOL!
I swore up and down until sixth grade(!!!!) that I believed because I thought that statement had a direct relation to the amount of presents I would receive.....so devious!!
DD6 started asking me questions at 4, but I answered her with questions. She'd ask who puts out the presents, and I'd ask, who do you think does it, etc. She thought it was us, but I'd never confirm it while I thought she was still uncomfortable with the idea.
She finally let me off the hook this year! On Black Friday I was out of the house by 5a.m., back by about 6:30. I thought everyone was still asleep, however, she came downstairs about 15 minutes later, sat next to me and said: "I know you put the presents under the tree". I'm still not sure where that came from, because I hadn't even taken the "goodies" out of the trunk of the car, yet somehow she knew where I had been and what I had been doing!!
I definitely agree that estimating a child's LOG, is just an estimate. In Mia's friend's case, I surely think the parent has more subjective evidence to place that child's LOG, than Ruf would have access to in a limited testing situation.
As a *soft* science, though, I still do find the categorizations useful. It's especially interesting to me as a parent, that my youngest seems to have a Ruf LOG that is higher than her WPPSI score would indicate..........
Neato