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.
Citation needed. Those are United States customary units per Wikipedia. Often incorrectly named Imperial units, but this is the first time I’ve seen it argued they are metric.
Also, The Metric Conversion Act happened in 1975, so not since the late 1800s. It also carves out that use of metric is voluntary.
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.