This is the answer from boost units: https://www.boost.org/doc/libs/1_78_0/doc/html/boost_units/FAQ.html#boost_units.FAQ.Distinguishing_Quantities_With_Same_Un

This is the answer from boost units: https://www.boost.org/doc/libs/1_78_0/doc/html/boost_units/FAQ.html#boost_units.FAQ.Distinguishing_Quantities_With_Same_Units https://www.boost.org/doc/libs/1_78_0/doc/html/boost_units/F... tl;dr is uses some sort of pseudounits to make dimensionally similar but incompatible units, well, incompatible.