(Also, if you answer more "F" now, then maybe it's just your inferior developing).
I also would have thought I was more sensory focused (sights and sounds, etc) and I think part of this, is the auxiliary simply not being differentiated yet. That's supposed to be in pre-teens. So the preference of N over S is not as obvious. Ultimately, I could see where I was more focused on fitting the sensory data into meanings, and not just experiencing it for itself.
This site has a test for children: http://www.personalitypage.com/html/kids.shtml
The page describing child types seems to be down, but it argues that the first letters to develop are E/I + J/P (the "sociability temperaments"), and then the third letter to develop (At around 6) will be the dominant function. The type code will be complete when the aux. develops.