There’s brutal grading in the first years in the basic premed classes.
OP can fashion a Chicago-like program at Harvard, or not. The appeal of UChicago is that you must take those hard classes, but it’s very bad for premeds.
90% is for students who make it through all the pre-reqs with a med school worthy GPA. But many don’t. (Everywhere, many don’t, but at UChicago especially since premeds can’t take easy classes to balance their oganic chemistry semesters, and may be placed in AP5Bio which can be devastating.)