The radii of the stars in this animation are not drawn to scale. The full horizontal scale is about 50 AU, while the radius of Sirius A is only about 0.01 AU and the radius of the white dwarf Sirius B is about 100 times smaller than that.
Thus, to scale Sirus A would only be about a pixel wide and Sirius B would be only a fraction of a pixel in width if the geometries were represented correctly. The geometries of the orbits are shown to scale, however.