Void Beam from Erasing Strike's "Regicide" not spawning on Lagon

As the title states, Erasing Strike’s node ‘Regicide’ which spawns a Void Beam when hitting a rare or boss enemy 100% of the time with 4 points does not appear to be spawning a void beam when hitting Lagon.

I was fighting Lagon in the Ending the Storm timeline, and I did not see any void beams spawn from hitting the boss. I tried looking for damage numbers, or watching his health bar to see if it was just invisible or under the terrain because of the boss’s weird hitbox, but as far as I could tell there was no damage being done at all.