Gas grenade and increased Grenade Damage, does it work?

Hey, I'm trying to upgrade my Crossbow. There is an affix "increased Grenade Damage" but in Path of building, it does not increase gas grenade damage at all. Gas grenade has "grenade" in it so logically it should increase the poison and hit damage.

Am I missing something? Is Path of building wrong that it does not calculate that damage for Gas grenade hit or poison DPS?