I actually did use their deal for this, it's now called the "Visit Argentina" pas (originally their "Argentina Travel" deal).
We used it for four flight legs. The main problem is that they use a hub and spoke model, with most flights flying in and out of Buenos Aires. So while we wanted to go from El Calafate to Iguazú Falls, to Salta, we had to go El Calafate to Buenos Aires, to Iguazú Falls, to Buenos Aires, to Salta. Each of those counts as a leg.
It's valid for 3-12 legs, and can be combined with their South American pass, for flights to other countries in the region.
My blog post about when we chose to use the "Argentina Travel" deal (now known as the "Visit Argentina" pass - we used it for four legs, from El Calafate, to Buenos Aires, to Iguazú Falls, to Buenos Aires, to Salta. However, we actually got a refund in the end on the Salta leg as they had flight cancellations, and we had to bus instead.