That's a stereotype, and complete misinformation.

Most germans in Argentina were Volga germans, regular Germans, Jewish Germans and antinazi Germans who arrived in different waves before WW2. The nazis who fled to Argentina are estimated to be 5,000 vs 1.6 million who moved there between 1919 and 1932. Argentina was chosen so a tiny number could hide among a large preexisting population of the same ethnicity, they are not the origin of that large number.

It's the same story with Italians: 2 million arrived between 1880 and 1920, before WW2. When fascism arose in Italy, immigration slowed down to a trickle. After the war only 380,000 arrived, a smaller number than the original wave and their descendants.