Harbinger's Shard Not Dropping in Beachhead Map/Boss?

So I've been doing a decent amount of T15 Beachhead maps lately. There's been something that I noticed from the runs that there hasn't been a lot of Harbinger's Shards not dropping as much during the boss. I get a lot of Horizon, Engineer, Chaos and the rare Annulment and Ancient shards. However, when it comes to the Harbinger's Shard, I rarely see them or never see them.

Is anyone else experiencing the same thing or is it just me not realizing that I'm actually getting them, but just not as much?

I don't think they drop in that map so it can't be self sustaining making new beachhead maps by just running them.