You do not need a business background. It certainly does not hurt to have one, but you shouldn't reorder your life or delay law school just to get one.
I'm not much of a gambling man, but I would wager that firms still screen at Penn.
Firms do have hard cutoffs even at CCN- even non-vault firms. Someone who is clearly bottom 10% is an autoding at most firms.
It amazes me how much law students think firms scrutinize every candidate. They interview hundreds of people, receive thousands of resumes, and screen almost wholly on law school grades/prestige.
They don't scrutinize every candidate, but they do scrutinize every serious candidate. At the firms I'm familiar with, hiring partners and hiring personal go through quite a bit of deliberation for candidates who make it to the callback level.