Hmm, it makes sense to me--the people living there are descended from those summarized and analyzed, and even if the veil is thin, it accords them the courtesy of privacy. (Also, obvs, no GMaps in 1977.) Like, if one is close enough to the town and inhabitants to be able to identify them from the book, one is invited to uphold the courtesy by the fact that a thin veil exists, and if not, their privacy is maintained anyway.