I think that these are just two separate weapons/gearing options.
One if a masterwork that you can gain through soldiery tomes ( weather xxxxx), and then restore to i110 (xxxxx).
The other you quest/collect items to get (relic atma) and then do more grinding/collecting to take to animus, and get the achievement.
Remember that they said that the would keep adding on to the quest for the Zodiac upgrade so it makes sense that it only goes as high as i100 initially. They have patches 2.25,2.23,2.35 to add quests and bring it up to/near High Allagan/restored Gerolt, before they raise the item level.
