You are confused, arguments about the benefits or lack thereof of metric are based on internal consistency, not standards and metrology. Nobody is arguing agai

You are confused, arguments about the benefits or lack thereof of metric are based on internal consistency, not standards and metrology. Nobody is arguing against more precise definition of standard values, which is why Imperial units these days are themselves defined in terms of SI units. So if the meter were to change, for example, so would the US foot.