Measures of academic productivity, like the h-index, m-index, i10-index are useful but imperfect. Their imperfections are more than an abstract concern. Hiring committees consider them in determining how the applicant stands in relation to his peers. The weight committees give to these numbers varies, especially with newer metrics.
How do we know which measurement of scientific productivity is the most accurate? This question suggests that no measure is accepted as generally accurate. The h-index has a retrospective validation for some fields. Have studies tracked a cohort of scientists over time to compare the ability of these measurements to predict who received a tenure-track appointment in the next five years? (I realize that is not everyone's goal. It is one that tenure committees care about.)