Ice Resistance bug? It’s not stacking properly

Are ice resistances not stacking properly? I’ve got the kuku enhanced ice resistant armor equipped, which should give +10 ice resistant, so I expect level 10 ice resistance in stats. It only seems to give +5 levels in stats. When you swap out pieces to check how it calculates the level, it gets even weirder with how the levels are calculated.

For example, equipping only my +5 ice resistant cloak seems to not give any increase in levels at all. If I equip it with my ice resistance armor it goes up to level 10, when it should be 15 levels ice resistance combined?

I’ve also noticed the same with frostward abyss gear not actually increasing the resistance level when socketed into armor. Are ice resistances not on a 1-to-1 ratio with levels?? It seems that fire does stack in a 1-to-1 ratio??

Am I missing something or is this bugged?