You don't have the yellow/gold border because you couldn't actually purchase the Hive Disruptor perk to fill all the bubbles. Technically, the perk is still there; it's just hidden. I noticed this on one of the after mission reports and saw that it was still assigning xp to that perk, even after it was disabled. It really doesn't affect the weapon much, to be honest. Hive Disruptor causes pretty low damage that I've seen thus far.
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Why Hive Disruptor still hidden in only this weapon?
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Because it seems it's the only weapon where Hive Disruptor interferes with its signature perk. White Nail requires 3 consecutive precision shots to activate. The problem with this being that Hive Disruptor is applied as an additional hit that can't do precision damage. This breaks the 3-shot streak.
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Because it wasn't working properly with the White Nail perk. It would nullify it, so they removed it temporarily. Not missing out on much damage either tho.