Depending on the system parameters, the transverse optical beam shift in
reflection can be non-Hermitian with real eigenvalues and non-orthogonal
eigenstates. We reveal that such an unusual resemblance with typical PT
(parity-time)-symmetric systems originates from the beam's momentum domain
polarization evolution. Specifically, for partial reflection, the momentum
domain inhomogeneous polarization evolution of the beam is at the heart of all
the peculiarities in the corresponding eigenspectrum of the transverse shift
operator. These findings put forward the notion of novel non-Hermitian
spin-orbit photonics and enable common polarization optical elements to act as
PT-symmetric non-Hermitian systems