Andrew Gideon wrote:
Some work was done on an airplane. The new W&B is of the "removed/added"
sort and computes a new empty weight and moment arm. But the document
doesn't state the gross weight.

The changes were all avionics; no airframe or power plant work was done. So
I'd expect the gross weight to remain unchanged from the prior W&B.

But does the new W&B need to state the gross weight, even if it is
unchanged? If not, do we then need both documents to cover the legalities
of documentation in the airplane?

I have never seen a W+B that didn't list the gross weight.