The majority of U.S. customary units were redefined in terms of the meter and kilogram with the Mendenhall Order of 1893 and, in practice, for many years before
Not redefined as ‘metric’. It means the base measurement is connected to SI along a fixed constant. Meters and kilograms are the base units for length and mass in SI, which is actually metric. The respective USCU units for length are inch, foot, yard, and mile and mass a really annoying number of things.
The systems of measurement are connected, but USCU is not metric.
From the article you linked
Not redefined as ‘metric’. It means the base measurement is connected to SI along a fixed constant. Meters and kilograms are the base units for length and mass in SI, which is actually metric. The respective USCU units for length are inch, foot, yard, and mile and mass a really annoying number of things.
The systems of measurement are connected, but USCU is not metric.