I just don't buy the Carbon Fiber vs Stainless construction. They aren't used for the same thing (low weight structural stiffness vs heat conduction, radiation & appearance).
From what I understand it was a water tank contactor that did the hopper in Boca Chica... and it will never face lanch/re-entry stresses. That won't replace anyone.
The starhopper( test article) is indeed made by a water tank contactor. The actual starship will be made by stainless steel in LA as confirmed by Musk on twitter. Also he mentioned something about stainless steel having better properties than cf.
The old BFR design had a large carbon-fiber hull, the new one has a stainless steel hull. Unless I'm missing your point, that's a major piece of the rocket that's no longer made with carbon fiber. (The giant molds that they were building for the BFR hull, for example, are now redundant.)
From what I understand, the plan is for the production Starship to have a stainless steel skin. I'm sure it will be a much more refined construction than the hopper, but skinned in stainless steel nonetheless.
From what I understand it was a water tank contactor that did the hopper in Boca Chica... and it will never face lanch/re-entry stresses. That won't replace anyone.