The easy test questions can become pretty hard.
If most people saw a grape, a banana, and an orange, and where asked which did not belong, most would pick the banana. But, its easy to argue that ANY one can be excluded based upon the many properties of the three items!!!
I think the problem lies in how the very high IQ kids were raised and the special sensitivities they bring to their interpretation of events. The ease of withdrawing into your own thoughts can certainly lead to living in a fantasy land.
The fact that these kids will gravitate to the purely intellectual and not get any experience in the real world may leave them without the skills to navigate the real world.
But, if they see it as something else to learn, then its no mystery.