Not to be Captain Obvious, but they needed the sling bar to utilize their own sling. The French assembled their own rifles at the end of the war and also added their own stacking rod to those. I own a handful of the French-assembled rifles but I am not the expert. All of mine were assembled postwar. I am guessing that a wartime rifle pressed into French service would need the sling bar, but would simply use an actual cleaning rod for stacking. Beyond that, I would think the French would have only made repairs as needed, so you likely would not necessarily see any other modifications on a wartime rifle. No need for a French star firing proof on a wartime rifle (unless rebarreled, etc.).
