McGraw does teach at Harvard but I’ve seen plenty of other books written by professors and they’ve been copyrighted to the author not the school they work for.
Does this copyright notice mean that Harvard owns the copyright rather than McGraw? If so, is it some unusual work for hire situation? Or maybe McGraw voluntarily gave Harvard the copyright as a gift?
There could be any number of reasons - including those you suggest.
Could also be that much of the research was done in conjunction with class preparation and done by multiple members of the faculty.
Perhaps this book was meant to be a textbook to be used for a specific class, in which case each person involved was doing this during school time and using school resources and staff. Most schools have specific rules and regulations about work product if it is done using their resources on their salary. Perhaps Mr. McGraw was simply the organizer of this book and assigned the details to others and did the final editing. Giving the copyright to the school would be fair.
Harvard owns the copyright. This can happen in several ways:
McGraw put together the book as part of his job duties at Harvard and the work was thus a work for hire.
McGraw voluntarily allowed Harvard to have copyright. This is more likely, and can be done for any number of reasons: as a thanks for the support, as a donation to the college, because he felt the copyright wasn’t worth keeping in his name, and probably a dozen more.
Harvard University Press insists on holding copyright for works it publishes. This is not unheard of for university presses, and even more common for magazines for a particular discipline. If McGraw wrote this book as a series of articles for a magazine published by the press, then they own copyright when they’re reprinted in book form.
The book may have been part of a seminar/conference, with the stipulation that any publication of the information be copyrighted in Harvard’s name.