The study by Wang emphasizes that "the application of the relativity principle is very tricky, not just manipulating Lorentz transformations". For example, when applying the relativity principle to the Maxwell equations in free space, one may directly obtain the constancy of light speed, without any need of Lorentz transformations. Another typical example is the "hyperplane" differential element four-vector in relativistic electrodynamics, which contradicts both change of variables theorem in mathematical analysis and Lorentz contraction effect in Einstein's special relativity, namely which follows neither the principle of classical mathematical analysis nor the principle of relativity.