I don't think I understand your criticism.

The etymological sense of the Pennsylvania Dutch phrase is in fact, as far as I can tell, 'high people' or 'fancy people'. This is not the literal meaning or connotation of the phrase in Pennsylvania Dutch today. I did not think (and the LLM did not claim) that the phrase is used in Pennsylvania Dutch with this meaning, or that it was borrowed from standard German at any time. Essentially, the LLM helped me find recognizable cognates to understand how the phrase originated.