@ucbalumnus, my frame of reference is mainly Texas publics because that’s where my son’s interest lies, but I wouldn’t call MIT’s credit policy “generous” by any means. Only 5s are considered, and only for a handful of exams. And the rep doing the presentation at MIT the day we toured made it very clear that there was only limited credit to be gained through AP, but MIT expects high school students to have taken a rigorous schedule including AP or IB classes if possible.
As a comparison, my son’s top choice school, UT Dallas, will award him 31 credit hours for the eight AP exams he’s taken so far (six scores of 5 and two scores of 4). At MIT for the same eight exams he will get nine unrestricted elective credits and he could place in a higher level introductory math. Perhaps MIT is generous relative to its peers, but I would not call it objectively generous at all, and MIT’s own rep said the credit was limited.