  We report studies of $k$-dependent Land\'e $g$-factor, performed by both
continuous media approximation k.p method, and atomistic tight-binding
sp$^3$d$^5$s$^*$ approach. We propose an effective, mesoscopic model for InAs
that we are able to successfully compare with atomistic calculations, for both
very small and very large nanostructures, with a number of atoms reaching over
60 million. Finally, for nanostructure dimensions corresponding to near-zero
$g$-factor we report electron spin states anti-crossing as a function of system
size, despite no shape-anisotropy nor strain effects included, and merely due
to breaking of atomistic symmetry of cation/anion planes constituting the
system.
