No one really knows what else Dr. MacKenzie might have worked on while in Argentina, besides The Jockey Club and Mar del Plata (since changed). But he was there for quite a while, and it's entirely likely he looked at other projects, such as the El Boqueron estate course which recently surfaced.
I have not heard his name connected with the city course, however. And there is the danger of his name being connected to many courses there by hearsay, whether or not he ever saw them, especially since his associate in South America, Luther Koontz, lived in the country and built courses there for many years afterward.
Whitten and Cornish's book is terrific but Ron didn't have much good documentation of MacKenzie's time in South America when it went to press.