I think the real tipping point question is this: Are they avoiding tough courses to protect their GPAs? Nothing could be more anathema to the mainstream University of Chicago ethic than that.
The impression I get from DS and friends is that this isn’t much of an option. You can take brutal classes or you can take sort of brutal classes. But easy A classes just don’t exist. Or if they do, they haven’t discovered them yet.
Worrying about GPAs is a real and valid thing now. Maybe it didn’t matter in the 60s or 70s when just surviving 4 years at UC was enough to get you into that PHD program you wanted. But today it matters. Whether we’re talking about IB, MBB, law school, med school, or a PHD program. GPA matters and you don’t get a pass just because you are at UC.
As a full pay parent I am very glad that he is concerned about his GPA. If he wanted 4 years just to explore passions and learn just for the sake of learning and not worry about grades, he could have done that for a lot less than $70,000 a year.