I cannot speak for the likes of QF but I used to be part of the selection panel for a very large UK airline and am quite familiar with the various tests used. What I can state, categorically, is the results of the tests were never used in isolation. They were only indicators of how a candidate might feel/react/perform. Having seen the results of the 'shrink' test, it was always up to the interviewers to then probe these facets of a candidates personality with specific questions. VERY often you would find the tests suggested something about a person which, on further investigation, would prove false. So it could well be that someone is tending towards Introvert but that would definitely not rule them out. So what if you're naturally a bit quiet. What does matter is what you're going to do when something needs to be said or done. This would be the type of questioning route that you would expect to be followed during an interview; so I'd want to know specific examples of when, for instance, something has gone wrong with a plan and you've intervened to rectify it or when you were part of a group and had to point out to the group leader that they were making a mistake...that sort of thing. Of course, you wouldn't just jump into that question. You'd start off by asking the candidate to tell us about a time they were involved in a group task, what they had to do and the candidates role in it. Having settled that, you'd then further it with questions about how the task progressed etc and then examine the 'going wrong' bits.
There were very often characteristics that needed further examination; lack of empathy, teamwork etc but I can only ever recall one introverted type that was unsuccessful because of this 'trait'. Essentially, he was SO shy, reserved and uncommunicative, that during the interview, when asked ANY question, he simply blushed bright red and didn't utter one word. It was the only interview that I'd ever had to cut short and the only interviewee that I saw the shrink tests get spot on.
In summary, I'd say don't sweat it. Think about times when you've had to speak up and did. That's what's important, not being the gob****e who talks so much nobody else can get a word in.