Dear P.,
you are completely right. Just to uncover this contradiction was one of the main purposes of my essay. I wanted to show, that the principal core of special relativity is semantically inconsistent if all deducable consequences are really deduced.
The invariance of the speed of light is certainly the most counterintuitive aspect of SR. No one really understood why the speed of light is constant regardless of the motion of the OBSERVER.
Mathematically this aspect is expressed by the relativistic composition law of velocity, in particular by the composition of the speed of light c with a subluminal (!) speed, that is, c = c v/(1 cv/c^2).
The same particular law can consistently be applied to a particle model of light. Accordingly, the speed of light is always the same regardless of the motion of the SOURCE. This conclusion may be equally counterintuitive like the Invariance of the Speed of Light but it is nonetheless in full agreement with special relativity.
This result allows for a relativistic emission theory theory of light. Taken together with classical kinematics, an emission theory makes the velocity of light usually different in different inertial frames of reference; but Einsteins result shows that relativistic kinematics eliminates this problem. Since emission theories of light were traditionally associated with particle models, this meant that a particle model of light is compatible with special-relativistic kinematics.
see also: Stachel, John; Einsteins Light-Quantum Hypothesis, or Why Didn_t Einstein Propose a Quantum Gas a Decade-and-a-Half Earlier? In: Einstein_The formative Years, 1879_1909, Einstein Studies 2000, p. 240
But this possibility has far-reaching consequences with respect to the internal consistency of Special Relativity: It means that f.e. the deSitter-Experiment can relativistically (!) be interpreted in two different way: the speed of light c depends on the motion of the source resp. the speed of light c does not depend on the motion of the source. Both relativistic interpretations are in principle possible.
In other words, Special Relativitiy has obviously a blind spot if its principal core is completely unfolded.
Kind Regards
Helmut