It’s the notion that “extroverts” aren’t capable of holding deep, intellectual conversations or that “introverts” are more prone to them. I accept that may not have been your intent, but it’s how I read that comment.
I fully agree with the second thing you said.
To be fair, I said "not willing" and not "not capable". There was probably a hint of bias coming from an introvert and personality type that doesn't generally feel heard.
But I think the more broad and modern personality models beyond introvert/extrovert are better for this rather than the broad strokes I painted with.
Probably what's being re-hit upon is that there's more to personality types than introvert and extrovert.