You are comparing apples to bagels. Harvard does not count withdrawals as drop-outs. Think of all the “famous” folks who left Harvard mid-way to start businesses or do other things. Their academic files are still active, and their studies can be resumed at any time- a year, a decade, twenty years later. This is Harvard’s nomenclature, which is why they have a 0% transfer out figure.
It is very hard to compare such small numbers across the top colleges, since how they classify “someone who started but hasn’t finished” can vary based on administrative policies and nomenclature.