There are currently 3 items in the game which scale off uncapped resistance: Urzil’s Pride, Frostbite Shackles, and the ruby fang set bonus.
Both the ruby fang set and Urzil’s Pride count generic elemental resistance as part of your uncapped resistance, but frostbite shackles do not.
How to reproduce: Get rings that give only elemental resistance, equip the three items, and add/remove the rings to see changes. To test ruby fang set you need to fish for breakpoints in poison stacks applied to dummy.