It’s less that “authoritarian” is made up, and more that it’s useless as a descriptor. Hitler and Mussolini represented the capitalist class and oppressed workers and other social groups. Socialist states represent workers, and oppress capitalists and fascists through land reform and collectivization. Both wield authority, but some for good and some for bad.

"Authoritarianism" is not a distinct mode of production, nor does it actually describe structures. It's like saying "bad" or "mean," it has a negative connotation but means almost anything.