Experimental results on molecular diffusion in supercritical methane over a wide pressure range reported by Ranieri et al. [Nature Communications 15, 4142 (2024)] are compared with the theoretical expectations based on the Lennard-Jones model. In the low-pressure low-density limit the kinetic approach within the Chapman-Enskog approximation is shown to be adequate. At higher pressures and densities the freezing density scaling approach becomes appropriate. We analyse the transition from the gas-like to liquid-like dynamical behaviour from the perspective of Stokes-Einstein-Sutherland relation between the coefficients of self-diffusion and shear viscosity. This analysis locates the Frenkel dynamical crossover close to the transition from gas-like to liquid-like molecular diffusion in methane observed experimentally. The reported results provide a useful practical tool to estimate the transport properties of supercritical methane in parameter regimes where experimental results

are not yet available.