As you can see, the weapon on the left has a 'Req. Lvl to equip' of 60, while the other one has Lvl 59. They both have the same Item Levels. Notice that there is no 'Reduced level requirement' affix on both weapons, so that possibility is scratched. Upon salvaging them, obviously, the one with lvl 59 lvl req turned into Wishful essence, while the other one of lvl 60 lvl req. turned to Exquisite Essence.
How is this so? Is this a bug of some sort? This new system is indeed confusing. I hope this could be resolved soon as people begin to pick up more magic items now for crafting mats for the 1.07 patch.