what makes it a carbide die set is that the set contains a carbide sizer die. Always been that way.
Carbide is very hard, more than enough to size pistol cases, its biggest advantage is that it has a low coefficient of friction with the cases, so lube isn't needed. That has always been the selling point of carbide sizer dies, not needed to lube the cases. Cases do need to be clean, or you could have issues.
They don't do a better job than steel sizers, they do the same job, easier (no lube, or lube clean up). Usually the carbide is a ring, cemented into the sizer die body. If your press can be set up so the shell holder contacts the carbide, it can crack and break. Avoid this.
Lubing the brass and using a carbide sizer doesn't hurt anything, I just don't see the point of doing both for normal pistol reloads.