The Mercenary can't quip gear!

As shown in the image above, the in-game explanation states that mercenaries with the Strength attribute can equip gear with Strength, Strength + Intelligence, or Strength + Dex. However, my mercenary is purely Strength-based(Earthshaker), yet cannot equip gear with Strength + Intelligence attributes(Garb of the Ephemeral!

Please fix this bug , if not please someone tell me why this happen?

backup image link:

https://imgur.com/a/mY777yh