Yeh it is strange. It's a typical adult guy's brain in there, right? Or does his condition directly affect the brain?
His life is very different to any (or 99%) of ours, as he's always been a small guy and I can't know how that influences someone's personality or psychological development. He probably can't enjoy many usual pleasures in life (like rollercoasters, having a normal job, competing in sports, playing physically in a typical way with guys his age, going to the shops independently and being able to reach the counter) so it makes sense he'd gravitate towards a different set of pastimes and sources of contentment and enjoyment. So he may not feel as we would, if shrunk and then treated the same way.
I'm glad a guy with a condition like that is able to make a living and do stuff.