MOTW Buff question.

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Pel
Core Lord
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Why doesn't bonus from Nih runes in armor/weapons apply bonus duration to the druid buff mark of the wild in the skill description it says
"Buff - invoke the power of the wild to strengthen self or target ally" "Innate skill not affected by skill level bonuses"
So in the description it's a buff but the duration doesn't get affected by Nih runes is this a bug or ?