Reaper: Bone Harvest doesn't stack with Dual Blades?

So I’ve tried Reaper and I noticed that dual-handed weapons doesn’t work with Nightblade’s Dual Blades, I mean Cold/Pierce bonus only, kind of shame because Inquisitor’s Ranged Expertise stacks with Rifles.

Is it intended?

Dual Blades only works with dual wield one handed melee weapons. So yes, it’s intended.