I [i]could[/i] imagine that this is because of the player only killing [b]Major[/b] versions of these enemies (those with yellow health bars). As far as I know, in the Taken events in Patrol, Taken Wizards, Knights and Centurions only spawn as Majors. Right now, out of my head, I cannot think of any location (outside of the Dreadnaught, which is TTK owners only) where these enemies spawn in their normal version. There are some issues regarding Majors and Grimoire Card counts, as mentioned in the original post. The Majors usually do not count towards Grimoire Cards. I'm not Siffow or a Bungie Employee at all, but could you please verify with your friend if he is only defeating Major enemies or also normal versions of these? That could help their investigations. Thank you!