Remember that IQ is a measure of intelligence. The MBTI S/N dichotomy measures practicality over creativity, which are two forms of intelligence. It's been said over and over again that IQ doesn't measure creativity.
The scientific community when it comes to psychometrics is biased. I haven't taken an IQ test (with a clinician in the room) in quite some time. But when a clinician is in the room, I would imagine that an IQ score is determined beyond multiple choice and problem solving questions.
When determining an IQ, do they also factor interests relative to age level into the equation? As in would a child with more intellectual or esoteric interests more likely have a higher IQ? If not, then why else would a clinician be overseeing the test-taking process?