What we could agree on is that interactions among the electrons (repulsion and antisymmetry) (appearing in "effective charge") make the difference.
With one single electron in a hydrogen-like ion, and neglecting corrections from relativity, finite nucleus size and so on, P protons make all orbitals P times smaller. The potential energy scales like P2 because the nucleus charge scales like P, and the kinetic energy scales like P2 because it depends on k2. All 3d 4s... orbitals, just scaled down, remain solutions of Schrö's equation, the sequence of energies is kept, and the world is simple.
The repulsion energy among electrons does not scale as P2 because they keep their charge q. If the orbitals kept their shape and scaled down by P, the electron repulsion energy would scale only by P. Changing P can't keep the solution for the same number of electrons, even if scaling the dimensions.
So the electronic configurations of Cr and Fe2+ may differ.