Can't upgrade dex skills with Jarngreipr Ringmail Gauntlets equipped

I have the unique gloves Jarngreipr Ringmail Gauntlets equipped which is supposed to allow Strength to satisfy melee skill requirements.

I'm using spear skills that require dex that the gloves should override, but every time I want to upgrade these skill the game makes me cut a new gem. I tried disabling the gem cutting warning already, it still just cuts a new gem rather than upgrading the existing one, where I've already invested jeweler orbs on.

Could you help with this? Or is this how it's intended?