I wouldn’t trust that data. The only data the university has officially released about the class of 2019 is this: http://chicagomaroon.com/2015/04/14/record-low-acceptance-rate-as-applicant-numbers-increase/
UChicago students are nerdy, not shut-ins. Being extroverted will not make you stand out (There are even frats and parties! Yes, plural!). I don’t know where you are getting the ridiculous idea that you will be a big fish in a small pond. UChicago is not a small pond in any conceivable way, and you would have be an absurdly big fish.