Ghalt's normal shot pierces immunity shield?

I noticed that when I played story mode Algorithm, I could shoot the Elite giant bot things when they put up their blue immunity shield (before stunning all within range) and actually deal normal damage. Is this intended? I could later test whether upgrades or abilities are also involved, but I just wanted to get this out there first.

I tested this a bit today.

Can pierce:

  • Unmodified shots.
  • Shots with tier 3 Pellet Party helix upgrade.
  • Shots with Pellet Party and Both Barrels Blazing.
  • Only 1 of the 2 shots fired with Slug Rounds and Both Barrels Blazing.

Cannot pierce:

  • All Dual Wield shots.
  • Shots with tier 3 Slug Rounds helix upgrade.

Again, by “pierce” I mean do full damage, not up to 10 per shot.

This really does seem to be a bug.