Board Thread:Theories and Speculation/@comment-34661853-20181111160651/@comment-734582-20181126072444

LoneNinja wrote: It's explicitly stated to be made of Hashirama's cells so, it's stated to be organic. It can be removed or added like a prosthetic arm. I don't think Naruto literally cut off his (zetsu) arm in order to graft the absorbtion prototype on it.

So whatever it is, while made of hashirama cells, it definitely has components that allow it to be attached and detached like a prosthesis. Which may impede with stuff like Wood Release. It could also be just Zetsu cells (which, i might add, were studied by Sakura and are much safer than straight hashicells), which have almost non-existent wood release.