The corky wings on twigs start in rough patches like the patches on the twigs here and expand as the branch grows. New growth is smooth, but "roughens up" as the twig lignifies. In a few growing seasons (or as few as one), twigs can have 1/2 inch tall ridges all along them.
FWIW, although the corky growth is most prominent in Ulmus Alata, it can also appear on other elm species. I've had corky growth on my cedar elm for years, although it's never very pronounced and can be easly dealt with (or even ignored, if the tree is big enough)