[2023] Hydroid's Plunder using old armor strip logic.

This is not actually a bug.

Plunder doesn't remove armor by itself at all.  What it does, is it removes the current stacks of Corrosion and locks in the armor reduction from Corrosion to make it permanent. So if you apply 5 Corrosion status then cast Plunder, then apply 5 more Corrosion, you're reducing their armor by a fraction of a fraction.  And you can just keep shaving off fractions until the value gets rounded off to zero (or more likely the enemy dies first).  Versus, applying 10 stacks of Corrosion is removing ALL their armor in one shot, there is no fraction left to carry over.  Corrosion acts on their maximum armor, but their maximum armor is being set to a new lower value each time you Plunder them.