Hi
I recently added a UV to my shield, giving me added elemental defence. None of my other equipment has elemental defence. However, when I hover on the summary icon (the mask in the bottom left corner in the character window) I cannot see any elemental defence at all (bar doesn't show). I have UVs on helmet and armor that shows up (shadow and freeze resistance), just not the shield one.
That how it works. It doesn't add to your defence, it doesn't protect your hp, it only protects the shields HP so it takes longer before it breaks.