Wait a minute! Is the micrometer actually used in service to measure dimensions with the smaller tolerance?
Good point, if the "tolerance" specified on the NC is what they are trying to measure on the part, then the gage is useless. If the tolerance is the gage tolerance, then there really is no basis for complaint (it just looks like a standard gage spec, see this) - the NC needs to identify the relationship to the part tolerance to be of an issue.