I believe that where it says you must return to your country to get the student visa is not updated, because the student visa is currently obtained while in Argentina and not in the Argentine consulate of your native country.
Also I might add that it is possible to study in the National Universities for free even if you´re a foreigner without getting a ´cupo´ (which is what is competetive). You can sign up directly to the university in the same inscription period as argentines. Unfortunately this requires legalizing your high school degree, which can only be done after taking 6 exams on ´formacion nacional´, basically 6 subjects from High School in Argentina. Few people are crazy enough to attempt such a thing