The writer is confused. It’s more Old High German. For instance, PA Dutch is simply a dialect of “Deutsche”.
I work with a guy who was raised Amish. He left the sect when he was about 20 and lives a normal American life, he’s about 50 years old now. He’s married with a couple of kids and a few years ago they hosted a German high school exchange student for a year. He could easily speak with her using his first language, Pennsylvania Dutch and her speaking German. She told him that his speech sounded to her like her grandparents speech.