When I transmog my one handed swords to fist weapon, fist weapons don’t appear at all when I am out of combat unless I press Z (it makes you pull weapons from your back as default)
Another scenario that they become apparent is when I am in combat and use skills. They appear for a few sec then disappear again.
I am not sure if this is intended or not but seems like a bug to me since it makes fist weapon mog completely pointless and confusing.
Additions, my monk is Draenei, talent spec Dps spec (I dont remember the name but Monk has just one dps spec). Lastly swords are heirloom swords.