The weapon Heavy Pick can't be dual wielded, despite being a Medium size weapon
it's smaller cousin, the Light Pick, however, can be dual wielded
This can be replicated by creating a new character of medium size and using the misty being to buy any weapon and testing them.
Other CEP weapons such as the heavy mace (also medium size) and light pick (small size) can be dual wielded, so it is odd why the heavy pick cannot be used akimbo.
Heavy Pick Statcard (shows it is medium and not large)
https://i.imgur.com/NhEJCRh.pngMe being unable to place it into my second slot
https://i.imgur.com/UnLp56n.pngNormally the slot will be highlighted with a white box outline
As it is a medium weapon I see no reason for it to not be dual wieldable. Other medium CEP weapons are able to be.