The article says that diamond (the material used for simulation) is a nondispersive medium. Diamond is an optically dispersive material, with a dispersion cons

The article says that diamond (the material used for simulation) is a nondispersive medium. Diamond is an optically dispersive material, with a dispersion constant of about 0.044 [1]. Does the article use dispersion to mean something different from optical dispersion? Or maybe they meant to say nondissipative (no energy loss during photon propagation)? [1] https://en.wikipedia.org/wiki/Diamond https://en.wikipedia.org/wiki/Diamond