  The neutrino mixing parameters are thoroughly studied using
renormalization-group evolution of Dirac neutrinos with recently proposed
parametrization of the neutrino mixing angles referred as `high-scale mixing
relations'. The correlations among all neutrino mixing and $CP$ violating
observables are investigated. The predictions for the neutrino mixing angle
$\theta_{23}$ are precise, and could be easily tested by ongoing and future
experiments. We observe that the high scale mixing unification hypothesis is
incompatible with Dirac neutrinos due to updated experimental data.
