Insofar as smokeless powder in a black powder gun, it is as much a function of no brass case surrounding and sealing the powder charge as it is the material the revolver is made of. It is the lack of the brass "safety blanket" that will get you, probably more so than the makeup of the steel.
When the brass case (which seals and directs the pressure of the ignited powder) in a cartridge gun fails, it most often leads to catastrophic action failure, with sometimes spectacular results and injury. Even older cartridge guns(Trapdoors, Peacemakers, S&Ws, Merwin and Hulberts,, etc., made for black powder loads, on the heels of the percussion guns can be safely fired with lighter loads of smokeless powder, thanks to their use of brass cases, though their steel is nowhere near up to modern standards.
Being as Uberti is owned by Beretta, and they make a wide variety of smokeless cartridge guns in the same factory, it wouldn't surprise me in the least, that like Ruger in their Old Army, Uberti uses the same modern gun steel for their black powder line as they do their cartridge guns. Especially since at least a couple of them have commonality between the smokeless and black versions, like the revolver carbine, and the Cattleman which comes in a percussion version as well as a cartridge version.