You may have both in your tritype. Sorry, thinking in the same time. 6 is said to be common for infjs, but said to be common for all. I didn't check if it makes it the most common type all.mbti types but there would be some logic. 6 equals a lot to live in fear to me (subjectively). Still studying. 3s are said to be more extroverts as a core while it says achievement mainly. That's what makes mes think it's inconsistent, to some point. I prefer to see what real people say.
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"Ever since I was a child, I’ve never allowed myself to get too close to people. I’ve avoided emotional attachment. Perhaps I’ve been so afraid of death and dying that any connection just seemed like a bad thing, something that wouldn’t last." Dana Scully - Christmas Carol.