I intend to travel from a non-Schengen country to the United States via air and transit through the Frankfurt Airport. I understand such transit does not require entry to the Schengen Zone, however the relevant presidential proclamation has
noncitizens of the United States (“noncitizens”) who were physically present within the Schengen Area
And so this is not clear: the transit area is legally not part of the Schengen Zone but is it physically?
For example this answer has
Airport transit areas are exempted from immigration regulations, but they are very much the country's property, under its authority and jurisdiction.