As a German I am a little bit confused about the statements and assumptions being made here.

No, Americans don’t communicate clearly, direct and context-free.
Quite the opposite in my experience.

But also: No, Germany isn’t low context, despite very direct communication and being on the low-context-side of the graph shown.
Depending on region, there are a lot of implicit rules and customs you just have to know about.

Imho it’s more complicated and not as black-and white as this theory wants to paint it.