I've worked with a few celebs over the years. Be them CEOs or models, they all have "people" to handling this stuff. I wouldn't be surprised to hear gates reads none of these books, that the entire scheme is handled by his PR. Worse yet, many extremely wealthy people believe "they" create things when they in fact pay others to do the real work. I'd need lots more evidence before I'd believe that someone like Gates is actually typing the words.
But even if he is reading these books, there is this from the OP:
"“‘We don’t have any say over what Bill chooses,’” she said “‘We just leave it on his desk and he reads what he wants to read.’” Ms. Kim lucked out"
They "don't have any say" except that they appear to be able to shortlist books. Getting your book onto the desk of a reviewer is 90+% of the effort needed to secure a review. The ability to place anything on the desk of a billionaire is the sort of influence for which people pay good money.