This is unfortunately not correct. German does not allow dual/multi citizenship except for specific pre-approved cases, or EU-citizenship. On the application form, you must state that you will renounce your other citizenship/s in order to get German. So essentially, the person who may have managed to keep a non-EU citizenship has not actually found a workaround, but has broken the law. I was able to keep UK citizenship but had to renounce NZ in order to get German citizenship (i have never been registered in Germany as a NZer, always as an EU-citizen. I still had to admit to any other citizenships, and renounce). Any person who keeps a non EU citizenship without prior approval has basically gained German citizenship illegally. I don't know how likely it is they can get caught, but they will be stripped of German if they are. I was handed this letter to make it absolutely clear to me that I couldn't just re-apply for NZ afterwards.