When putting a loaded map in your off hand your off hand disappears and the map is the only thing loaded in the off hand.

When putting a loaded map in your off hand your of hand disappears but the maps still loaded.

Actual result:

While holding a loaded map your off hand should be loaded while holding loaded map.

How to reproduce

Put a loaded map in your off hand then look closely to the bottom left corner and you should see that the off hand is not loaded in.