Your own quoted article says "1.2 million persons had been born in Germany, 5 million had two native-German parents, and 6 million had one native-German parent." "Many more had distant German ancestry. During WWII, the United States detained at least 11,000 ethnic Germans, overwhelmingly German nationals.[3] The government examined the cases of German nationals individually, and detained relatively few in internment camps".

So millions with German ancestry, detained some who were German nationals and only a few in internment camps.