That headline is comically misleading and just bad journalism.
Of course it benefits so few since according to the article there are only 3414 full time undergrads on aid at Stanford. vs. the 19.2 million total college students.
Did the author expect that Stanford was going to pay for college for non-Stanford students?
The relevant metric is of those 19.2 million college students how many would the program have benefited IF they got into Stanford. I expect that the number would be very, very high.