I think AS can lead to atypical behavior for type, in addition to possibly making the ego feel weak; especially from the problems fitting in socially. For an INTP, with inferior Fe, hat will be particularly damaging, and when the ego feel really threatened, that's when the "daimonic complex" will likely constellate, which for us would be Fi. So that's another reason (beside the brain lateralization I've mentioned elsewhere) that you might seem to have a lot of Fi.
(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.