One hand to two

[Melamoto]

They can be physically wielded in one hand is untrue. They are two handed weapons. I think you would need monkey grip and oversized two weapon fighting to be able to do that.
All double weapons are two handers so with out some sort of feat/multiple limbs you can not do what you want to do.

If so, then why does it include a specific clause about what happens if you wield a double weapon one-handed?