Protection from X Potion

[Gregor]

Gregor acquired some Protection from X Potions recently, where X is Fire, Cold, Acid, Lighting, and such.

In the gnoll chef quest, Gregor used the Protection from Cold Potion before facing the ice mephits and the Protection from Fire Potion before facing the fire elementals.

In both cases, Gregor still took cold/fire damage. I don't know for sure, but it looked as if it was the full elemental damage. The combat logged displayed no indications that there was any damage resistance or damage immunity taking effect. There was also no change to Gregor's reflex save vs. the elements.

[Gregor]

Is this fix retroactive? Will it affect potions that are currently in people's inventory or only newly created/spawned potions?