That's BS.
The first time he used the sword he was able to easily take all of his haki back into his body.
As you can see he's always been able to do that.
The purpose to enma is for Zoro to improve his CoA haki control and his ability to gather large amounts of haki easier and faster.
Enma didn't give him the ability to cut Kaido. It's funny that people still push that when the Scabbards can cut Kaido and they are nowhere near as powerful or as skilled Zoro. They can't even use enma.