  Gorbatenko & Neznamov [arXiv:1301.7599] recently claimed the absence of the
title problem. In this paper, the reason for that problem is reexplained by
using the notions of a unitary transformation and of the mean value of an
operator, invoked by them. Their arguments actually aim at proving the
uniqueness of a particular prescription for solving this problem. But that
prescription is again shown non-unique. Two Hamiltonians in the same reference
frame in a Minkowski spacetime, only one of them including the spin-rotation
coupling term, are proved to be physically non-equivalent. This confirms that
the reality of that coupling should be checked experimentally.
