No, there's nothing odd about the fact that units based on one set of measures become fractional when expressed in units of another measurement system. It just shows that neither is based on the other.
And of course "the fractional scale is not unique to US Customary Units", since there is no fractional scale within that measurement system. Nor within any other, AFAIK. Your pound consists of an integer number of ounces (right?) and your foot of twelve-point-zerozerozero... inches. The "fractional scale" exists only between measurement systems. (AFAIK. Except maybe old British currency, that was really weird, I'd trust those crazy Englanders to have about six Pi pennies to the shilling or something.)
https://frinklang.org/frinkdata/units.txt is one of the things i find myself reading and using to complain about things. Frink is a conversion tool and calculator, like "how many grains of rice worth of calories is needed to boil 1 liter of water" and even more esoteric stuff. It also can correctly convert between most of the esoteric units (rods, hogsheads, furlongs).
Frink has phone apps, so you don't need a data connection as you would with wolfram alpha or google.
Naah. It's defined in terms of the second, nowadays, but it's based on the circumference of the Earth: The meter was originally defined as one ten-millionth of the distance between the equator and the poles.
And of course "the fractional scale is not unique to US Customary Units", since there is no fractional scale within that measurement system. Nor within any other, AFAIK. Your pound consists of an integer number of ounces (right?) and your foot of twelve-point-zerozerozero... inches. The "fractional scale" exists only between measurement systems. (AFAIK. Except maybe old British currency, that was really weird, I'd trust those crazy Englanders to have about six Pi pennies to the shilling or something.)