The 'Freight couplers' that the author feels are 'backward' are more advanced than the couplers we use in our conventional trains. Only a few European countries and countries that were historically under British influence use screw couplers. Modern railways across the world use various types of CBC couplers ( some variants of which are used in IR's freight and passenger stock). And jerks are a problem with CBC rakes, something which has not not been fully controlled so far. While improvements have been made to the point where these are barely perceptible, the problem is a difficult one to control fully.