  Recent investigations have found that the strongly constrained and
appropriately normed (SCAN) meta-GGA exchange-correlation functional
significantly over-magnetizes elemental Fe, Co, and Ni solids. For the
paradigmatic case, bcc Fe, the error relative to experiment is $\gtrsim 20 \%$.
Comparative analysis of magnetization results from SCAN and its
\textit{deorbitalized} counterpart, SCAN-L, leads to identification of the
source of the discrepancy. It is not from the difference between Kohn-Sham
(SCAN-L) and generalized Kohn-Sham (SCAN) procedures. The key is the
iso-orbital indicator $\alpha$ (the ratio of the local Pauli and Thomas-Fermi
kinetic energy densities). Its \textit{deorbitalized} counterpart, $\alpha_L$,
has more dispersion in both spin channels with respect to magnetization in an
approximate region between 0.6 Bohr and 1.2 Bohr around an Fe nucleus. The
overall effect is that the SCAN switching function evaluated with $\alpha_L$
reduces the energetic disadvantage of the down channel with respect to up
compared to the original $\alpha$, which in turn reduces the magnetization.
This identifies the cause of the SCAN magnetization error as insensitivity of
the SCAN switching function to $\alpha$ values in the approximate range $0.5
\lesssim \alpha \lesssim 0.8$ and oversensitivity for $\alpha \gtrsim 0.8$.
