  Relativistic treatment of the finite speed of light correction in absolute
gravimeters, as evolved by Rothleitner and Francis in Metrologia 2011, 48
442-445, following the initial publication in Metrologia 2011, 48 187-195,
leads to spurious conclusions. The double Doppler shift implemented in the
gravimeters obliterates the difference between its relativistic and
non-relativistic formulation. Optical heterodyning used in Michelson-type
interferometers makes the quadratic Lorenz-like term of the double Doppler
shift discernable against the linear term, while in relativistic experiments
the quadratic term has to be detected against the unit. The disturbance of the
registered trajectory caused by the finite speed of light includes tracking
signal delay as intrinsic part not reducible to the Doppler shifts.
