What you are saying quite likely has some truth in it, Grace. But I can tell you this: many extroverted children often grow very little compared with introverts. Introverts blossom and become more balanced, being able to straddle equally both characteristics of personality, whilst extroverted people tend not to 'go within' and find out more about themselves. It's the introverts who ask themselves the profound questions of life.
I would say I was fairly introverted and a bit of a 'loner' as a child, but according to a few Myer-Briggs tests done between forty and fifty I was right at the centre almost, just leaning towards the now 'Extrovert' end of those cross hairs. I'd blossomed.
The way I see it, the Introverted part of me got me reading, writing and thinking. Then at thirty-six I took up public speaking with Toastmasters and have been with them ever since. I now feel completely comfortable meeting strangers - yes, and even talking in front of audiences of 200 people or more.
Don't knock the Introverts. People like Lord Bertram Russel and Albert Einstein were probably introverts.