Interesting but not entirely convincing link between being introverted or extroverted and self confidence. That probably deserves a little more nuance. Confidence in which ability? I'd like to read more on that.
Of course, extreme cases of introversion (or extroversion) are pathological, but not on the normal scale of things.
I wonder if it's similar to this article about the church of interruption. https://sambleckley.com/writing/church-of-interruption.html
I won't pretend to speak for all introverts, but for me it's not at all a matter of waiting for an invitation (why should I ever?), but rather that I need to choose the conversations carefully, because they drain rather than energize me. I have a number of conversations "available" each day before I'm drained and need to recharge by - what makes me an introvert - not interacting with people.
But if the subject at hand is interesting or important enough, I will absolutely partake in the discussion and will absolutely not wait for an invitation. Self confidence has exactly nothing to do with me being an introvert.