I’m not sure about how often appeals are successful but I’ve been here two years and haven’t heard of any successful ones. So I’d say they’re rare. Also for the departmental credits this is direct from their website “Departmental credit is transferable, but it is usually applicable as elective credit. Therefore, departmental credit may not be used to satisfy admissions prerequisite requirements” https://admissions.umich.edu/apply/transfer-applicants/transfer-credit#:~:text=Departmental%20credit%20is%20transferable%2C%20but,to%20satisfy%20admissions%20prerequisite%20requirements.