There was absolutely nothing unusual about this. This happens all the time in instances when the airline knows there will be limited J demand but lots of Y demand. You'll see it in the summer time to Europe from the US when there's less business travel but more demand for family vacations and whatnot, and apparently here, where Argentines are now on a school break. This stuff plays out every single time with lots of regularity on every single airline. You just happened to notice it, for whatever reason. In general, they'll clear all eligible upgrade into J, make sure all confirmed revenue customers are accommodated (some will be upgraded if there aren't any seats left in Y and there are some in J), and process all NRSA in order of seniority/ priority once all revenue customers are accommodated.