I had the same conversation with a friend in college too about not living in my head.
This was rather uncharacteristic of DD. She lived very much in her head between age 2 and 3.10 or so but these days, she's all about having fun. I do wonder if it pops up once in awhile because she still think about these things once in awhile or she now processes ideas internally and only shares when she has a crystalized thought in her head.
I think I found her a friend who would enjoy talking to DD about the universe and other abstract ideas. It'd be interesting how that friendship would develop.