Interesting subject indeed - one which I very much hope to return to in some detail when time permits.
Briefly, I was one of those people who created these tests. I worked on them betwen 1972 and 1975 when they were the cutting edge of profiling.
They were never intended to be used this way, entrepreneurs hijacked them and business fashion, especially the growth of HR, hugged them to their eager breasts. It is a huge money making enterprise.
Strafer is correct in every respect. Until I have time to add to this thread just cling onto your conception of introvert and extrovert as a black and white differential. It is actually far more subtle than that with many shades and is the reason why I was involved in the creating and testing of vast question banks, each validated on thousands of people.
Strafers smoke and mirrors apply directly to these commercial tests, the meanest of snapshots large amounts of money can buy. They are easily fooled and anyone can be trained (for money) to place their personality into the 'acceptable' spectrum.
Regards
Rob