Rive converted to Void isn't getting any bonus from Vitality?

Rive is converted (base damage) to Void damage via Temporal Warrior.
It now has the Void and Melee tag.
Void Knight is Mastered.
Void Knight mastery says “you gain 1% more melee Void damage per +3 Vitality”.

Yet any additions to Vitality does nothing to the Rive tooltip damage.

The added damage works for Void Cleave and Erasing Strike which are Void Knight mastery skills, but also does nothing if you take Vengeance and convert it to Void.

Is this intended, i.e. that the more void melee damage from vitality only applies to Void Knight skills? because if so, that should be clarified in the text I think… Or is this unintended?

It might just be that the Void Knight bonus isn’t factored into the DPS tooltip. And the reason why you see a change on Void Cleave and Erasing Strike tooltip DPS with a change in Vitality is most likely due to the fact that those two skills both have the Vitality tag and directly scale with Vitality. While Rive (and Warpath) do not inherently scale via Vitality but Strength, even when their void conversion is applied.