I just checked and the system shows zero IAD-EZE saver awards in any class for the entire month of June. I suppose it's possible that all the awards were already booked but it seems unlikely. Maybe there's a glitch on united.com for that route because I'm always looking and almost never see any seats available. I had no problem last year when I needed an F saver award in April.
Benefits that can't be verified don't feel very real. On the other hand, 25% more miles for awards and new fees for services that cost United nothing feel very real.