I've known of some really introverted people back in school. They are people who don't say much unless talking about something they are interested in and often don't give a damn of what other people think of them. Shy and introverted aren't the same thing. I have an ISFJ friend who is very timid but I would say that there are plenty of people more introverted than she is- she enjoys social contact enough that she's far from a recluse but it takes a lot of effort to get her to talk but it's clear it's due to social anxiety.
"Uber introversion" and "staying at home" are definitely not the same things.
I find (because I wasn't able to get a job this summer) that I am spending a lot of nights at home but I know I'm not introverted and would rather be doing something else. My main social contact is either going on AIM, spending time with family (A lot of time actually!) or hanging out with the few people I actually enjoyed hanging out with in high school.