@Gina as a mixed up Austro-Germanic-Slavo-American, I can only confirm the German stare is indeed a real phenomenon and also shared by Austrians and even Swiss to a lesser degree. I have sought an explanation and until now I can only scratch my head. I do feel that Germans have next level abilities on soul penetration.

In the Austrian context, I thought its about figuring out how you know a person so you know the correct greeting to use. On the metro "are they a neighbor or just look familiar?"