Not sure if Ezskin would explain why, it replaces the shader tree to avoid the problem nodes. I would point to BBs response above, specular causes problems not just between FF and SF but also other apps (eg Poser to Vue).

Below is an illustration of the problem and not intended to be taken as a correct solution (I don't have BBs indepth understanding of the math).
I replaced the Anisotropic node (more commonly used for hair highlights) with the ks_microfacet node and reduced the about of spec returned. The eyesurface would also need to have this change for the full effect.