least $10^{-5}$ times smaller than the typical neutrino mass scale, in the absence of any intermediate scale between electroweak scale and $M_{\rm Pl}$.

-   there can be new contributions to charged lepton mass matrix of the type $\phi_{Ni} (Y^{'}_1 \overline{L_{\alpha}} H e_{\beta})/M_{\rm Pl} $ which can be suppressed by an additional factor $u/M_{\rm Pl}$ compared to the leading order contributions to charged lepton masses. But such corrections can, in principle, lead to deviations from diagonal charged lepton mass matrix. Usually, the leptonic mixing matrix is given in terms of the charged lepton diagonalising matrix $(U_l)$ and light neutrino diagonalising matrix $U_{\nu}$ as $U = U^{\dagger}_l U_{\nu}$. In the simple case where the charged lepton mass matrix is diagonal which is true in our model at tree level, we can have $U_l = \mathbb{1}$. Therefore we can write $U = U_{\nu}$. But $U_l$ may become non-trivial after the corrections are added and it will mimic as a correction in the leading order leptonic mixing which is TBM type.

-   there can be corrections to the Dirac neutrino mass matrix of the type $\phi_{Ni}(Y'_3 \overline{L_{\alpha}} \tilde{H} N_{\beta}) /M_{\rm Pl}$ which can again be suppressed by an additional factor $u/M_{\rm Pl}$ compared to 