Genie, no, it is not. Shortbread is much richer.

The slave-po' sharecropper shortnin' bread was flour (often corn), lard and/or drippings, perhaps salt, prepared stove-top in a skillet with lid, and served hot with molasses or sorghum syrup. It was rapid, and satisfyingly filled empty stomachs. Also look for saltin' bread in the threads linked above.

In thread 20217 (linked above, recipe search) a few attempts were made at recipes, but when eggs, refined sugar, spices, etc. get into it, one is stepping into the realm of the more affluent, or more recent cookery. It is doubtful that anyone in America has made or eaten the shortnin' bread of the desperately poor since the days of the Great Depression.