After extensive testing, it seems Upper Bound does in fact not work for the attribute it's applied to. It does correctly limit the effect duration to whatever the highest value is you received from an item, but not the intensity. I thought this might be due to "Multiple upper bounds are additive" but even setting the upper bound lower than the attribute (2 -> "<=1") had no effect.
**Tested with: **
-
Swimming Speed (60sec, 50%)
SwimmingSpeed: 50% Upper Bound: "<=50%" -
InvincibilityDuration (60sec, 2)
InvincibilityDuration: 2 Upper Bound: "<=2"


