These tough dogs dont resemble anything of typical DDR type in looks, besides the very well known Ex v Riedstern; but do have the attitude of what DDR type dogs were initially bred for; Strength hardness and courage..
yes you are right, they have straight backs as opposed to the DDR type and that's not the only difference in build. Temperament wise they are very much alike, calm when in "passive mode" but with a very good "mood switch", very civil dogs. NOTHING like the West dogs though, where we're talking smaller size and loads and loads of drive.
One would need to know the history of these dogs in order to better understand the differences between the types.