I'm working on trying to complete the Striking Distance Triumphs for both my Hunter and Warlock and it's been taking forever (like weeks). So I tracked the bounty and started tracking kills on screen vs. what the Triumph records. It consistently records n-1 kills per grenade. It rarely records more than two kills if you kill multiple enemies with it. Sometimes it records ZERO kills, even if you kill multiple enemies. I have in-game recording of this happening in Expedition, Gambit, and Patrol in the EDZ.