The dungeon journal does not accurately reflect the 25man mechanics, specifically total annihilation and catastrophic anomaly.
There's a parsing error in the Dungeon Journal that's causing some text that should be present in the 10H/25H versions of the entry to not show up. We'll see what we can do about fixing it.
But yes, for reference, Total Annihilation must hit 3 targets on 25H, or Catastrophic Anomaly will occur.